A Safety and Immunogenicity Comparison of 12 Acellular Pertussis Vaccines and One Whole-Cell Pertussis Vaccine Given as a Fourth Dose in 15- to 20-Month-Old Children
Objective. To compare the safety and immunogenicity of 12 different acellular pertussis vaccines combined with diphtheria and tetanus toxoids (DTaP) with one licensed diphtheria, tetanus, and whole-cell pertussis vaccine (DTwP) as a fourth-dose booster in children who had previously received DTaP or DTwP primary vaccinations.
Methods. Healthy 15- to 20-month-old children were enrolled at six National Institutes of Health Vaccine Treatment and Evaluation Units. All had been randomly assigned to receive three primary doses of DTaP or DTwP at 2, 4, and 6 months of age as part of an earlier National Institutes of Health multicenter trial of DTaP vaccines in the same Vaccine Treatment and Evaluation Units. Parents recorded the occurrence and magnitude of fever; irritability; and injection site redness, swelling, and pain for 3 days after vaccination. Sera obtained before and 1 month after the booster vaccination were analyzed for antibody to pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbriae (FIM), and pertactin (PRN). Diphtheria and tetanus toxoid as well as PT neutralizing (Chinese hamster ovary cell) and whole-cell agglutinating antibodies were measured on a subset of sera.
Results. A total of 1293 children contributed fourth-dose reaction data. Reactions were less frequent after DTaP than after DTwP. For children vaccinated with a fourth dose of DTaP, which was the same DTaP as received in the primary series, fever and injection site redness, swelling, and pain increased in prevalence compared with the third dose in the primary series. For children receiving DTaP as a fourth dose, injection site redness and swelling occurred more frequently in DTaP-primed than in DTwP-primed children. Variation in the occurrence of reactions among DTaP vaccines was observed.
A total of 1160 paired pre- and postvaccination sera were available for analysis. Serum antibody concentrations before boosting were lower than those obtained 1 month after the primary immunization. After the fourth dose, significant increases in antibodies directed against the included antigens were observed for all vaccines; postbooster vaccination antibody titers differed significantly among the DTaP vaccines. For children primed and boosted with the same DTaP, antibody levels were not directly related to the quantity of antigen included for PT, FHA, and FIM; for PRN, there was a closer relationship. Some DTaP vaccines given as fourth-dose boosters elicited antibody to PRN or FIM in some vaccinees, although the DTaP vaccines were not reported to contain these antigens; these responses were observed more frequently in DTwP-primed children. Agglutinin antibody rises were observed in all groups immunized with four doses of a DTaP vaccine containing FHA or PRN, regardless of whether the vaccine included FIM. Diphtheria and tetanus antibody levels exceeded the presumed protective concentration (0.1 IU/mL for diphtheria and 0.01 IU/mL for tetanus) after the fourth dose for all vaccinees.
Conclusion. Although differences were observed in reaction rates among the DTaP vaccines given as a fourth dose, the DTaP vaccines were, in general, associated with fewer adverse events than a US-licensed DTwP. For DTaP vaccines, fever; irritability; and injection site pain, redness, and swelling occurred more frequently after the fourth dose than after the third dose of the same vaccine in the primary series. No DTaP was consistently most or least reactogenic or immunogenic. Although serologic correlates of pertussis immunity are not defined, it is clear that most DTaP vaccines can stimulate comparable or higher serum antibody responses than DTwP for those antigens contained in the vaccine.
- adverse reactions
- diphtheria-tetanus-pertussis vaccine
- pertussis vaccine
- whole cell
- whooping cough
On July 31, 1996, the licensure by the US Food and Drug Administration of the first acellular pertussis vaccine combined with diphtheria and tetanus toxoids (DTaP) for use in infants as a primary series at 2, 4, and 6 months of age began a new era in routine childhood immunization against pertussis. Licensed DTaP vaccines are considered a preferred alternative to traditional diphtheria, tetanus, and whole-cell pertussis vaccines (DTwP) because they are associated with fewer local and systemic reactions.1-4 For several years, two licensed DTaP vaccines have been recommended for use in the United States as the fourth and fifth doses for children 15 to 20 months and 4 to 6 years of age, respectively,5,6 who had received a primary series with DTwP. The introduction of DTaP vaccines for infant use increases the importance of studies that evaluate the reactogenicity and immunogenicity of DTaP vaccines when administered as boosters to toddlers.
To evaluate the safety and immunogenicity of DTaP and DTwP vaccines given as a fourth dose, a double-blind, multicenter clinical trial of 12 DTaP vaccines and one US-licensed DTwP vaccine was conducted. All children had previously received three primary doses of one of 13 DTaP vaccines or one of two DTwP vaccines in a randomized, primary series trial7,8; one DTaP vaccine (LP-3P) was not available for additional study. The primary goal of the present study was to evaluate the safety and immunogenicity of 12 DTaP vaccines and one DTwP administered as a fourth dose in children who had received the same vaccine in the primary series. Additionally, the United States is in the midst of a transition period between exclusive use of DTwP and the anticipated exclusive use of DTaP, a period in which many children have received or will receive DTaP vaccines as boosters after DTwP primary immunization. The previous primary series study included a large number of children who received DTwP, and we took the opportunity to evaluate the safety and immunogenicity of the 12 DTaP vaccines given as a booster in a subset of those children. We report here on the reactogenicity and immunogenicity of a fourth dose of DTwP in children primed with DTwP, a fourth dose of DTaP in children primed with DTwP, and a fourth dose of DTaP in children primed with the same DTaP. This is the largest clinical trial to date evaluating booster immunization with DTaP vaccines from different manufacturers.
DTaP vaccines containing one to four pertussis components plus diphtheria and tetanus toxoids were included in the study (Table1). All the DTaP vaccines included pertussis toxoid (PT); most also included filamentous hemagglutinin (FHA), and some included pertactin (PRN) and/or fimbriae (FIM). There are at least two fimbrial proteins; one vaccine contained a single FIM (denoted by the identifier F1), and three vaccines contained two fimbrial proteins (denoted as F2). The DTaP vaccines differed in the source and quantity of included antigens and their methods of manufacture including toxoiding of PT, in the concentrations of aluminum as adjuvant, and in the quantity of diphtheria and tetanus toxoids (Table 1). Additional details of vaccine composition are described elsewhere.7
Healthy children 15 to 20 months of age who had completed an earlier multicenter trial conducted at six National Institutes of Health (NIH)-sponsored Vaccine Treatment and Evaluation Units (VTEUs) that compared these same 12 DTaP and WCL vaccines when administered at 2, 4, and 6 months of age as a primary series were offered participation. The protocol was approved by institutional review boards at each collaborating institution. Informed consent was obtained from parents or guardians before enrollment. No subjects with contraindications to immunization specified in the Report of the Committee on Infectious Diseases of the American Academy of Pediatrics (Red Book)6 were enrolled, and only those who received all three primary study doses in the earlier trial7 were eligible to participate.
The vaccines were evaluated at six NIH-sponsored VTEUs located at Baylor College of Medicine, Houston, TX; Johns Hopkins University, Baltimore, MD; University of Maryland School of Medicine, Baltimore, MD; University of Rochester, Rochester, NY; St Louis University School of Medicine, St Louis, MO; and Vanderbilt University School of Medicine, Nashville, TN. Children who had been randomized previously to receive 1 of 13 DTaP vaccines as a primary series at 2, 4, and 6 months of age7 received that same DTaP vaccine as a fourth-dose booster in the current study at 15 to 20 months of age (the one exception was that previous recipients of LP-3P were given LPT-4F1 as the booster) (Table2). Children who had been randomized previously to receive a primary series of DTwP manufactured by Lederle Laboratories (WCL) were rerandomized to receive 1 of the 12 DTaP vaccines or WCL as the fourth dose (Table 2). Those who received DTwP manufactured by Massachusetts Biological Labs (WCM) in the primary series were also rerandomized to 1 of the 12 DTaP vaccine groups.
Investigators, patient care nurses who collected the reaction data, participating clinicians, and laboratory personnel were blinded to vaccine group identity. Vaccine vials were labeled with letter codes, were of a single lot, but not always the same lot, as given in the primary series, and were not identified by type or manufacturer. Nurses who administered vaccine had no other contact with patients or parents to help ensure blinding. Study vaccinations were given in the thigh (0.5 mL with 1-inch needle). Children were given oral polio vaccine concurrently. Haemophilus type b conjugate vaccine was not administered concurrently.
Reactions were assessed as described previously.8 Parents were provided an electronic thermometer (model 2013 M, Lumiscope Company, Edison, NJ), rated accurate to ±0.2°F (0.1°C), a gauge for measuring the size of local reactions, and reaction assessment forms. Reactions assessed included rectal temperature (fever defined as temperature ≥100.1°F); drowsiness (defined as unusually sleepy or inactive), use of antipyretics, irritability (scored as normal; periodically more irritable than usual but having normal activity [mild]; prolonged crying and refusal to play [moderate]; or persistent crying and could not be comforted [severe]); anorexia (defined as an unusually poor appetite); vomiting (as differentiated from spitting up); redness and swelling (each measured in millimeters using the gauge provided); and pain (scored as none, minor light reaction to touch [mild], cried or protested to touch [moderate], or cried when leg moved [severe]). Parents were asked to record assessments of each of these reactions daily before bedtime the day of vaccination and at bedtime for two additional evenings after vaccination. For scaled reactions, the maximum observed reaction that occurred during the specified time interval was recorded. The reaction assessment forms contained space for narrative recording of comments, other reactions, or any physician visit during the 2 weeks after vaccination.
A nurse contacted each child's parents by telephone on the first and third days after vaccination to review reactions and to check for the occurrence of severe adverse events. One year after booster vaccinations, a supplemental clinical history was obtained by study nurses to assess for any severe adverse events, hospitalizations, or other notable medical problems including developmental delay; seizures; other neurologic problems; failure to thrive; and diagnosis of pertussis, prolonged cough, or other serious infections.
Because no single laboratory had resources to perform serologic assays on all study sera, antibodies to PT, FHA, PRN, and FIM were measured by ELISA9 studies at three collaborating laboratories. For children primed with one of the DTaP vaccines, the primary serologic analyses are based on pertussis ELISA studies performed at Vanderbilt University (Dr Edwards) on sera from a randomly selected subset of children (∼45 per group); data results are presented for those children who completed the study per protocol (n = 32 to 44 per group). Pertussis ELISA studies for the balance of sera from DTaP-primed children were performed at the University of Rochester (Dr Pichichero). For all DTwP-primed children, pertussis ELISA studies were performed at the Center for Biologics Evaluation and Research (CBER) of the USFDA (Dr Meade). All three laboratories used the same assay protocol,9 reference sera, and method of calculation (reference line method10) to compute unitage. ELISA results were expressed in ELISA units (EU)/mL relative to US Reference Pertussis Antiserum (human), lot 3 (for PT, FHA, and FIM assays) and lot 4 (for PRN assay).9 The lower limits of detection as determined in the CBER laboratory9 were 2 EU/mL for PT and FHA, 6 EU/mL for PRN, and 3 EU/mL for FIM ELISA antibody determinations. The lower limits were reported to be similar in the other two laboratories and, therefore, for convenience these limits were applied to results from all three laboratories.
As an assessment of assay comparability among laboratories, 78 sera from the Vanderbilt sample and 28 sera from the Rochester sample were also assayed at the CBER laboratory. For these sera, interlaboratory correlation coefficients were determined for the four ELISA studies. Pearson correlation coefficients exceeded 0.90 for all comparisons except the CBER versus Vanderbilt comparison for PRN (r = 0.83) and the CBER versus Vanderbilt comparison for FIM (r = 0.88). Although these results indicate similarity of assay systems, correlation coefficients are incomplete indicators of assay comparability.11Additional analyses revealed systematic differences in antibody quantitation, comparable with those reported previously,9,11 and lower agreement for sera of low antibody concentration. Therefore, results are presented without combining results from different laboratories. Geometric mean concentrations (GMC) of pertussis antibody are presented from the CBER and Vanderbilt laboratories; the percentage of individuals with a fourfold or greater increase in antibody concentration are reported from all three laboratories because these analyses are less dependent on absolute quantitation.
Functional pertussis antibodies were determined by Chinese hamster ovary (CHO) cell toxin neutralization assay on a randomly selected 20% subsample of serum pairs at Vanderbilt University for DTaP-primed children and at St Christopher's Hospital for Children (Dr Deforest) for DTwP-primed vaccinees.9 Results were expressed as reciprocal dilutions, with the lower limit of detection at a 1:40 dilution.
The microagglutination assay was performed on a randomly selected 10% subset of sera from DTaP-primed vaccinees at Vanderbilt University and 10% of DTwP-primed vaccinees at CBER, using standard methods.9 Each assay used a 1:8 starting dilution, and results were expressed as reciprocal dilutions.
Diphtheria and tetanus antibody levels were measured on a 10% subsample of all serum pairs in the laboratory at St Christopher's Hospital for Children. Diphtheria antibody was assayed by toxin neutralization in VERO cells.12 Tetanus antibody was measured by a modified passive hemagglutination assay.13Diphtheria and tetanus antitoxin titers were converted to IU/mL by standard techniques.14
Every vaccination for which a reaction form was available was included in the analysis. If no information was recorded on the form for a given reaction and observation time, the reaction was considered to be not present at that observation. All reaction variables were treated as categoric; cutpoints for redness and swelling of >20 mm and for temperature ≥100.1°F were established. For the final data summaries, five key reactions (fever, irritability, injection site redness, swelling, and pain) shown previously to reflect common reactions after DTaP and DTwP vaccination15 are presented. Maximal reactions were determined by scoring each reaction as present if it had been noted at any time within the observation period of interest and tabulating the maximal reaction within that period for scaled reactions. Between-group comparisons of reaction prevalence were evaluated by χ2 or exact tests, as appropriate. McNemar's test was used to evaluate changes in rates of reactions from third to fourth vaccinations within each vaccine group.
To be included in serologic analyses, a child had to be vaccinated at 15 to 20 months of age and have sera drawn both before and after immunization (20 to 91 days after vaccination). For each serologic assay, GMC levels of antibody, SE values, and 95% confidence intervals were calculated for each vaccine group. Serologic calculations were performed on logarithmically transformed data, reporting the antilogarithm; results below the lower limit of detection for the assay were assigned a value of half the lower limit of detection. An individual was reported to have a fourfold or greater increase in antibody if the postimmunization value was at least four times the preimmunization value and at least four times the lower limit of detection. Between-group comparisons of GMC levels were made by analysis of variance; groups whose means did not differ significantly were identified by a modified Bonferroni procedure.16Within-group comparisons for the DTaP vaccines were made using the Wilcoxon signed-rank test. Comparisons of fourfold responses were evaluated by χ2 or exact tests. The Spearman rank correlation coefficient was used to assess associations between postprimary and pre-fourth-dose GMC levels and between-vaccine antigen content and GMC levels. Multiple linear and logistic regression were used to evaluate the possible role of VTEU, gender, and prevaccination PT antibody level on the postvaccination antibody to PT.
For all analyses, two-tailed P values < .05 were considered statistically significant. Unless otherwise stated, reportedP values were not adjusted for multiple comparisons. Calculations were performed using SAS (SAS Institute, Inc, Cary, NC) and StatXact-Turbo (CYTEL Software Corp, Cambridge, MA).
Of the 2264 children who completed the primary series trial,7,8 1374 (60.7%) continued in the current study. DTaP vaccine became licensed and available for the fourth-dose indication just before initiation of our trial; access to DTaP vaccine without study participation and the two venipunctures required for antibody analysis in the study accounted for most dropouts in our study. A total of 1352 (98.4%) of 1374 of the enrolled children contributed reaction data; however, we excluded from the analysis children who had received their primary vaccination series with WCM (N = 59; Table 2), because only children vaccinated with WCL were included in most analyses of reactions and immune responses in our earlier primary series trial.7,8 An additional 136 children were dropped from the immunogenicity evaluation; 33 children (2.4%) received vaccinations outside the time interval specified by the protocol, 39 (2.9%) had their postvaccination sera obtained <20 days or >91 days after the booster, and 64 (4.7%) were dropped for multiple other reasons, eg, failed phlebotomy and lost to follow-up. Therefore, 1160 children (90%) were included in the serologic analysis.
To assess the reactions observed after these fourth-dose boosters, we first examined the data from the following three groups: 1) children who received a three-dose primary series of a DTaP vaccine followed by a fourth dose with the same DTaP vaccine, hereafter designated the DTaP/DTaP group (n = 1087; group also includes LP-3P-primed infants boosted with LPT-4F1); 2) children who received a three-dose primary series of WCL followed by a fourth dose of 1 of 12 DTaP vaccines, hereafter designated the WCL/DTaP group (n = 190); and 3) children who received a three-dose primary series with WCL followed by a fourth-dose booster with WCL, hereafter referred to as the WCL/WCL group (n = 16). The small size of the WCL/WCL control group provides limited statistical power to detect potential differences between reactions after DTwP and DTaP vaccines. To facilitate presentation of the data, we first examined the aggregated results of all the DTaP vaccines compared with WCL with regard to representative reactions15 (Fig1, Table3), and then we present summary results for the individual DTaP vaccines (Fig2).
The proportion of children who had the indicated reaction on each of the three evenings after inoculation is shown in Fig 1. Adverse reactions developed in a similar pattern with time after the booster injections for all three groups. In general, fever, irritability, and injection site pain were maximal on the first evening, whereas injection site redness and swelling were maximal on the second evening (Fig 1) and all five of the key reactions declined by the third evening for all three vaccine groups.
For the three study groups, rates of representative reactions after the fourth dose were compared (Table 3). When WCL/WCL vaccinees were compared with DTaP/DTaP vaccinees, the following reactions were observed significantly less frequently in the DTaP/DTaP group: any irritability, any injection site redness, any injection site pain, moderate or severe pain, and severe pain. No significant differences were found for prevalence of vomiting, anorexia, and use of antipyretics (data not shown); however, the power to detect possible differences was low because of the small sample size in the WCL/WCL group. When WCL/WCL vaccinees were compared with WCL/DTaP vaccinees, the following reactions were observed significantly less frequently in the WCL/DTaP group: any irritability, any injection site redness, redness >20 mm, any swelling, swelling >20 mm, any injection site pain, moderate or severe pain, and severe pain. Among the children who received DTaP as a fourth dose, some reactions were influenced by the vaccine received for primary immunization. Any injection site redness, redness >20 mm, any swelling, and swelling >20 mm occurred significantly more frequently in children who received DTaP in the primary series (DTaP/DTaP group) than those who received WCL in the primary series (WCL/DTaP group) (Table3).
In the primary series for both DTaP and WCL recipients, any fever and fever >102°F and any redness significantly increased in prevalence with successive vaccinations8; for DTaP recipients, significant increases in any swelling were also observed.8 To assess whether this trend for intensifying reactions would continue into the fourth-dose booster, we compared reaction rates between the third vaccinations in the primary series8 and the fourth-dose boosters (Table 3). Because the incidence of reactions from vaccination to vaccination is not independent,17 we identified the subset of participants from the primary series trial who participated in the current study and included in the comparison of reaction data only those children who provided reaction data from both the primary series trial and this booster trial. For the DTaP/DTaP group, any fever, fever ≥101.1°F, fever >102°F, any irritability, any redness, redness >20 mm, any swelling, swelling >20 mm, any pain, moderate or severe pain, and severe pain were all significantly more frequent at the fourth-vaccine dose compared with the third-vaccine dose; drowsiness was significantly less frequent after the fourth dose (third dose, 12.1%; fourth dose, 7.1%; P < .001). For the WCL/WCL group, there was a significant increase in injection site pain; however, there was no increase in the frequency of fever, irritability, redness, or swelling. This group, however, included only 16 children and provides limited power to detect either increases or decreases in reaction rates. Comparisons were not made for the WCL/DTaP group because a different vaccine was administered at fourth dose than at third dose (Table 3).
Special attention was focused on monitoring for more severe reactions. None of the children in the study experienced a seizure, hypotonic/hyporesponsive episode, fever >105°F, or other uncommonly reported event associated with pertussis vaccination. Table4 presents the frequency of the selected reactions for each of the vaccines: severe injection site pain, severe irritability, and very large injection site redness (>50 mm) and swelling (>50 mm). Redness >50 mm occurred in 16 (1.5%) DTaP/DTaP vaccinees, all on the second or third day, and in 1 (6.3%) WCL/WCL vaccinee, on the third day. Swelling >50 mm occurred in 41 (3.8%) DTaP/DTaP vaccinees, all on the second day, and in 2 (12.5%) WCL/WCL vaccinees, on the second or third day (Fig 1). No WCL/DTaP vaccinee had redness >50 mm or swelling >50 mm. In the DTaP/DTaP group, severe irritability was reported for 12 (1.1%) and severe injection site pain for 8 (0.7%) of vaccinees. In the WCL/DTaP groups, severe irritability was reported for 3 (1.6%) and severe pain for 2 (1.0%) children. In the WCL/WCL group, severe pain was reported for 3 (18.8%) children and no severe irritability was reported. No DTaP vaccine was distinguishable as producing these severe reactions more often.
Next, we examined the proportion of children who had the indicated common reactions by the third evening after inoculation for the individual DTaP booster vaccinations compared with each other and with WCL (Fig 2). For DTaP/DTaP vaccines compared with each other, significant variation in prevalence was observed only for redness (P < .001) and swelling (P < .001). The percentage of children with any redness ranged from 13.5% to 47.1% and with any swelling ranged from 11.3% to 38.6%. No significant variation was observed for any reaction among the WCL/DTaP groups except for fever ≥102°F (P < .05). Four (18%) of 22 WCL/PM-2 vaccinees, 1 (14%) of 7 WCL/BSc-3P vaccinees, and 1 (13%) of 8 WCL/Por-3F2 vaccinees had fever ≥102°F, respectively, compared with none in the other groups.
The 1-year safety follow-up did not reveal any unusual or unexpected events. Specifically, there were no unexplained deaths, hospitalizations, or chronic illnesses.
Prebooster Pertussis Antibody Levels
For all vaccine groups, antibody concentrations significantly decreased from those measured after primary immunization (7 months) to those measured before the fourth dose (Tables 5-9). For PT antibody in those children who participated in the booster study, postpriming series GMC levels for the DTaP vaccines ranged from 19 EU/mL (LPT-4F1) to 182 EU/mL (BSc-1); in comparison, prebooster antibody levels ranged from 2 EU/mL to 14 EU/mL, respectively (Table 5). Similar observations occurred for FHA, PRN, and FIM (compare Tables 6-9 with reference 7). There was a significant, positive correlation (r > 0.76,P < .002) between the postprimary and prebooster GMC levels of antibody to PT, FHA, PRN, and FIM, as measured by ELISA.
Postbooster Antibody Responses to PT
All of the vaccines produced significant rises in antibody to PT. However, postvaccination GMC levels differed between the DTaP/DTaP and WCL/WCL groups (Table 5) and did not correlate with the PT antigen content of the vaccines (Tables 1 and 5). For the randomly selected subset of children who received four doses of the same DTaP vaccine whose sera were tested in the Vanderbilt laboratory (Table 10, part A), the percentage of vaccinees with fourfold responses differed among the vaccine groups (P < .001) and ranged from 48.8% to 100%. For the group that received LPT-4F1after a primary series of LP-3P, 40.5% of children had a fourfold increase in PT antibodies. Similar percentages of individuals with fourfold rises were seen for the subset of children whose sera were tested in the Rochester laboratory (Table 10, part B).
Children who received WCL in the primary series responded to the pertussis toxoid contained in the DTaP vaccines administered as a fourth dose (Table 9). Comparisons between the DTaP/DTaP and the WCL/DTaP vaccine groups must be made cautiously because assays were performed in different laboratories and because sample sizes in the WCL/DTaP vaccine groups are small. However, PT priming by WCL is suggested by the observation that for 11 of the 12 DTaP vaccines, the GMC for the WCL/DTaP group was higher than for the DTaP/DTaP group. For the WCL/DTaP vaccine groups, the percentage of vaccinees with fourfold responses to PT ranged from 63.6% to 100% (Table 10, part C), but the percentage was not significantly different among the vaccine groups. For the WCL/WCL vaccine group, 93.3% of vaccinees had a fourfold response to PT (Table 10, part C).
After adjusting for vaccine group (DTaP only), with multiple linear regression analyses, we did not find vaccinee gender, race, or VTEU enrollment site to be associated with post-anti-PT antibody levels. Postbooster anti-PT antibody levels were positively correlated with preboost anti-PT levels (P < .001).
Postbooster Antibody Responses to FHA
For those children who received DTaP in the primary series, all the DTaP vaccines containing FHA produced significant rises in antibody to FHA after the fourth dose (Table 6); postimmunization antibody levels were not significantly correlated to the quantity of FHA in the vaccine (Tables 1 and 6). Significant differences among the DTaP vaccines were observed in postimmunization FHA antibody concentration (Table 6). For the randomly selected subset of vaccinees whose sera were tested in the Vanderbilt laboratory, fourfold antibody rises to FHA were observed in at least 80% of vaccinees for all DTaP vaccines containing FHA (Table 10, part A). For those children who received four doses of the same DTaP, the percentage with fourfold rises in FHA antibody was not significantly different among the vaccines containing FHA. Generally, similar results were observed for the children whose sera were tested in the Rochester laboratory; however, somewhat lower percentages of fourfold rises were observed for children immunized with Mich-2 and CLL-4F2 (Table 10, part B). For the WCL/WCL vaccine group, 13.3% of vaccinees had a fourfold response to FHA (Table 10, part C).
In the primary series trial, few of the children developed antibodies to FHA after vaccination with WCL.8 In this fourth-dose study, WCL appears to have been less effective at priming for an FHA antibody response than DTaP vaccines containing FHA. Specifically, for all 10 DTaP vaccines containing FHA, the postimmunization GMC in the WCL/DTaP groups was lower than in the DTaP/DTaP groups (Tables 6 and9). For the children in the WCL/DTaP vaccine groups who received a vaccine with FHA, the percentage of children with fourfold antibody responses to FHA differed among the vaccine groups (P < .001) and ranged from 16.7% to 94.1% (Table 10, part C); for only 5 of the 10 DTaP vaccines with FHA was the percentage at least 80%. Only 13.3% of the WCL/WCL vaccinees had a fourfold antibody response to FHA, and although a statistically significant rise in antibody to FHA was observed, the postvaccination GMC was only 5.8 EU/mL (Table 9).
Postbooster Antibody Responses to PRN
For those children who received DTaP in the primary series, all four DTaP vaccines containing PRN produced significant rises in antibody to PRN after the fourth dose (Table 7); antibody levels were significantly correlated (P = .001) to the quantity of PRN in the vaccine (Tables 1 and 7). Significant differences among the DTaP vaccines were observed in postimmunization PRN antibody concentration (Table 7). For the DTaP vaccines containing PRN, fourfold antibody rises to PRN differed among the vaccine groups (P < .05) and were observed in 78.1% to 97.7% of the vaccinees in the DTaP/DTaP groups whose sera were tested in the Vanderbilt laboratory (Table 10, part A).
WCL appears to have been approximately as effective at priming for a PRN antibody response as DTaP vaccines containing PRN. For the four DTaP vaccines containing PRN, the postimmunization GMC in the WCL/DTaP groups was similar to that in the DTaP/DTaP groups (Tables 7 and 9). In the WCL/DTaP vaccine groups, 50% to 90% of the vaccinees had a fourfold antibody response to PRN (Table 10, part C) when given a DTaP vaccine with PRN. There was no significant difference among the DTaP vaccines with PRN in the percentage of children with fourfold rises in PRN antibody. Children primed and boosted with WCL produced significant rises in antibody to PRN after the fourth dose, and 53.3% had a fourfold antibody response (Tables 9 and 10, part C).
There was evidence for PRN antibody responses in some children immunized with vaccines not reported to contain PRN. A significant rise (Table 7) in PRN GMC was observed for children who received four doses of CB-2 or SKB-2, vaccines reported to contain only pertussis toxoid and FHA. However, the biologic significance of these increases is uncertain because the postimmunization GMC levels were similar to or less than the lower limit of detection of the PRN ELISA (6.0 U/mL). Analyses were performed to determine whether the percentage of individuals with a fourfold rise to PRN varied among the eight DTaP vaccines without PRN. Significant differences among the vaccines were observed for the samples assayed at Vanderbilt (P = .012) and at Rochester (P = .012). The vaccine with the highest percentage of responders at Vanderbilt (Table 10, part A) was CB-2 (12.8%), and at Rochester (Table 10, part B) was SKB-2 (14.3%). In the children who received DTaP without PRN after WCL priming, a significant rise (Table 9) in PRN GMC was observed for SSVI-1, CB-2, and Mich-2 vaccines. The largest increase (from 7.8 to 32.8 EU/mL) was observed for CB-2. There was a significant difference (P = .0013) among the vaccines without PRN in the percentage of children with fourfold rises after WCL priming; for CB-2, 6 (31.6%) of the 19 children had a fourfold or greater rise in PRN antibody (Table 10, part C).
Postbooster Antibody Responses to FIM
For those children who received DTaP in the primary series, all four DTaP vaccines containing FIM produced significant rises in antibody to FIM after the fourth dose (Table 8). A general relationship between FIM content and FIM postimmunization GMC was observed (Tables 1and 8); however, the correlation did not reach significance (P = .051). The postimmunization FIM antibody GMC for LPT-4F1 was significantly less than the GMC for the other three DTaP vaccines containing FIM (Table 8). For the randomly selected group of children who received four doses of the same DTaP vaccine and whose sera were tested in the Vanderbilt laboratory (Table 10, part A), the percentage of vaccinees with fourfold responses differed among the vaccine groups (P < .001) and ranged from 72.1% to 97.4%; similar percentages were observed in the Rochester subgroup (Table 10, part B).
Children who received WCL in the primary series responded to FIM when they received a DTaP vaccine containing FIM (Table 9). WCL priming for a FIM response is suggested by the observation that for all four DTaP vaccines containing FIM, the GMC for the WCL/DTaP groups was higher than for the DTaP/DTaP groups (Tables 8 and 9). In the WCL/DTaP vaccine groups, fourfold antibody responses to FIM were observed in 72.7% to 100% of the vaccinees for DTaP vaccines containing FIM (Table 10, part C). There was no significant difference among the DTaP vaccines containing FIM in the proportion with a fourfold rise in FIM antibody. The WCL/WCL vaccine group produced a comparable GMC and fourfold antibody response to that of the WCL/DTaP vaccine groups for DTaP vaccines containing FIM (Tables 9 and 10, part C).
Antibody responses to FIM were examined for the eight vaccines not reported to contain FIM. A significant increase in GMC (P = .033) was observed after the fourth dose of the CB-2 vaccine; however, the mean pre- and postimmunization values were below the lower limit of detection for the assay (3.0 EU/mL). There were no significant differences among the vaccines not reported to contain FIM in the percentage of children with a fourfold rise for either the Rochester or Vanderbilt laboratory. In the children primed with WCL, significant increases in postimmunization GMC were seen after a booster dose of the following DTaP vaccines: BSc-1, CB-2, Mich-2, and PM-2. There were significant differences among the DTaP vaccines without FIM in the proportion of children in the WCL/DTaP groups who had a fourfold rise in FIM antibody. Of the 19 children primed with WCL and boosted with CB-2, 12 (63.2%) had at least a fourfold rise in FIM antibody (Table 10, part C).
Functional Antibody Responses
Postbooster vaccination levels of agglutinin (AGG) antibody did not relate closely with the quantity of FIM contained in the DTaP vaccines (Tables 1 and 11) or with antibody to FIM (Tables 8 and 11). The highest AGG titers were observed after immunization with the DTaP vaccines that contained the greatest amounts of FIM (Tables 1 and 11); however, GMC AGG titers >30 were observed for several DTaP vaccines that neither contained FIM (Table 1) nor induced an antibody response to FIM (Table 8). For the vaccines without FIM, significant rises in agglutinating antibody occurred after the fourth dose for all vaccines that contained FHA or PRN.
Antibody Responses to Diphtheria and Tetanus Toxoid
After the fourth-dose booster, all vaccines produced antibody levels in response to the diphtheria and tetanus components that exceeded the level presumed to be protective (0.1 IU/mL for diphtheria and 0.01 IU/mL for tetanus)18 (Table12). Diphtheria and tetanus antibodies were measured only for a small number of children, and no differences in postimmunization GMC levels were observed among the study vaccines.
This study provides a perspective on the frequency of adverse reactions and the level of antibody produced for different primary and fourth-dose DTaP and DTwP vaccinations. Before 1991 in the United States, DTwP vaccine was used exclusively for both the primary series of pertussis vaccinations and the fourth-dose booster. With US licensure of DTaP vaccines for the fourth-dose booster in December 1991 (LPT-4F1) and August 1992 (CB-2) and their recommended use,5,6 we entered the present transition period in which some infants who have received their primary vaccination series with a DTwP thereafter receive a DTaP vaccine as a fourth-dose booster. On July 31, 1996, the first DTaP vaccine (CB-2) and later, the second (LPT-4F1) and the third DTaP vaccine (SKB-3P) received US licensure for the primary series. Licensure of additional DTaP products is expected. In 1997, widespread use of DTaP vaccines as fourth-dose boosters in children who have received a primary vaccination series with a DTaP has occurred. Within the study reported here, we have evaluated the reactogenicity and immunogenicity of a fourth dose of DTwP in children primed with DTwP, a fourth dose of DTaP in children primed with DTwP, and a fourth dose of DTaP in children primed with the same DTaP.
Overall, the following observations can be made for pertussis vaccination-associated reactions when these vaccines are given as a fourth-dose booster:
As in the primary series study,8 we found DTaP vaccines were associated with lower rates of common local and systemic reactions than were DTwP vaccine (Table 3). This reduction was observed whether the children were primed with three doses of the same DTaP vaccine as used for the DTaP booster or primed with three doses of WCL and boosted with a DTaP.
The DTaP/DTaP groups did not differ significantly with respect to producing fever, irritability, or injection site pain after vaccination but did differ with respect to injection site redness and swelling. Additionally, as was observed in the primary series vaccination trial,8 although there were differences among the acellular vaccines, none was consistently the most or least reactogenic.
Some reactions occurred more frequently after the fourth dose of DTaP than after the third dose of DTaP. The frequency and severity of fever, redness, and swelling have been observed to increase significantly from vaccination to vaccination in the primary series with DTaP vaccines individually8,19,20 and among all DTaP recipients combined.8 In the present study, booster vaccinations showed a similar trend for intensifying reactions from dose three to dose four (Table 3). Because prebooster vaccination antibody levels were generally low, we found no correlation between the local reactions and prevaccination antibody levels for the DTaP vaccines (data not shown).
For some reactions, the observed frequency after DTaP as a fourth dose was lower in children who received a primary series of DTwP than in those who received the same DTaP for primary immunization. Specifically, any injection site redness, redness >20 mm, any injection site swelling, and swelling >20 mm occurred more frequently in children who received DTaP in the primary series than in those who received WCL in the primary series (Table 3). We examined the data for selection bias in the WCL/DTaP group to determine whether possibly fewer WCL primary recipients with severe reactions in the primary series trial participated in this fourth-dose study, but this was not the case. It must be noted that pooled over all four doses, fewer reactions occurred in the DTaP/DTaP group than in the WCL/DTaP group.
For the reactions reported here, there were differences in temporal patterns detected in our study. After the fourth dose of WCL or DTaP, fever, irritability, and injection site pain were observed most frequently on the first evening, whereas redness and swelling were observed most frequently on the second evening (Fig 1). In some individuals, the largest local reactions were observed on the third evening. For redness and swelling, an immunologic mechanism (Arthus reaction) is suggested by the timing of the reactions and by the increase in frequency at fourth dose.
Each of the evaluated DTaP vaccines produced significant increases in antibodies directed against included antigens, but postvaccination antibody levels differed significantly among the DTaP vaccines. Mean antibody levels stimulated by DTaP vaccines were highly correlated to the quantity of PRN antigen included in vaccines containing PRN, but there was no significant correlation between antibody response and the content of pertussis toxoid, FHA, or FIM. After the primary series of vaccinations, antibody responses to FHA, PRN, and FIM were correlated to DTaP vaccine antigen content for these DTaP vaccines.7 Because serologic correlates of protection are not known, it is impossible to determine whether any or all of the DTaP vaccines have achieved a protective level or whether the greater quantity of antibody generated by one vaccine when compared with another has any clinical relevance. Nonetheless, most of the DTaP vaccines tested, when administered as a series of four doses, were able to stimulate antibody responses to antigens in the vaccines that were similar to or greater than those observed after four doses of a commercial DTwP vaccine.
The immunogenicity results produced three unexpected observations in this study:
For PT, PRN, and FIM, but not for FHA, priming provided by a primary series of WCL appeared to be at least as effective as that induced by the same antigens in the DTaP vaccines. However, comparisons between the DTaP/DTaP and the WCL/DTaP vaccine groups must be made cautiously because assays were performed in different laboratories and because sample sizes in the WCL/DTaP vaccine groups are small.
An AGG response was observed after fourth-dose immunization with several vaccines (BSc-3P, SKB-2, PM-2, Mich-2, CB-2) that did not induce an AGG response after primary immunization.7After the primary series, AGG titers were observed only for those vaccines that induced either anti-FIM or anti-PRN, or both. For the two-component (PT and FHA) vaccines after fourth-dose immunization, the AGG response was observed in the absence of a response to PRN or FIM, suggesting that FHA may serve as an agglutinogen under certain conditions. Additional studies on the possible role of FHA as an agglutinogen are warranted and should include measurement of AGG titers in more children. As with the primary series, the highest AGG titers were observed after immunization with vaccines containing FIM.
An antibody response to antigens not reported to be in the DTaP vaccine was observed in some vaccinees when certain DTaP vaccines were given as a booster; such responses appeared to be more common in WCL-primed children than in DTaP-primed children. This observation is illustrated by responses to the eight vaccines in the study that were not reported to contain FIM. For one of these vaccines, there was a significant but quantitatively small increase in FIM antibody after the fourth dose of the same vaccine (DTaP/DTaP groups) (Table 8); however, among the children who were primed with WCL, four of these vaccines produced a significant increase in FIM antibody after the booster dose (WCL/DTaP groups) (Table 9). Those children who received the CB-2 vaccine as a booster after a primary series of WCL responded most frequently to components not reported to be in the vaccine; among the 19 vaccinees, 6 (32%) had a fourfold increase in PRN antibody, and 12 (63%) had a fourfold increase in FIM antibody. These observations suggest that some of the vaccines not reported to contain PRN or FIM contain small quantities of these antigens. The content of PRN and FIM generally was insufficient to induce a response in those who received only the DTaP vaccine, but sufficient to induce a response in some children previously primed by WCL vaccine.
Now that the first DTaP vaccines have been licensed for the primary series in infancy, fourth-dose boosters in DTaP-primed recipients will likely become the standard of care in 1997 and beyond. This extensive, comparative evaluation of multiple DTaP products under a standardized protocol, using standardized reaction assessments and serologic analysis in six independent NIH VTEUs should prove very useful in characterizing the expected vaccine-associated reactions and immune responses from the fourth doses of different DTaP vaccines in DTaP-primed children. This study suggests that some reactions may occur more frequently after a fourth dose of DTaP than after the first three doses of DTaP; nevertheless, the rates for DTaP vaccines were less than those for DTwP vaccines.
Significantly higher efficacy has been demonstrated for three DTaP vaccines (SKB-3P, BSc-3P, and CLL-4F2) compared with a US-licensed DTwP vaccine manufactured by Connaught Laboratories when administered as a primary series (at 2, 4, and 6 months, according to the US schedule of vaccinations).19,20 In trials in Sweden19 and Italy20, fourth-dose boosters were not given. Declining efficacy for the Connaught DTwP vaccine was apparent by the time vaccinees were 1 year old, indicating the need for a booster according to the recommended US schedule. In contrast, the DTaP vaccines studied maintained their efficacy to the end of the designed follow-up when vaccinees were ∼18 to 24 months old. The results of the Swedish and Italian trials,19,20 viewed in light of our observations here on reactogenicity and antibody response after fourth doses of DTaP vaccines at 15 to 20 months of age, suggest the need to evaluate the optimal timing of booster immunizations as well as the importance of evaluating the reactions and antibody levels with DTaP vaccines administered at 4 to 6 years of age as a fifth dose. Children participating in this National Institute of Allergies and Infectious Diseases-sponsored trial have now reached the age for the fifth dose of vaccine. In collaboration with vaccine manufacturers, the safety and immunogenicity of a fifth dose of DTaP and WCL vaccines are being evaluated in this population.
This work was supported by Contracts NO1-AI05049 (Rochester), NO1-AI15096 (Maryland), NO1-AI05051 (St Louis), NO1-AI72629 (Baylor), NO1-AI02645 (Vanderbilt), and NO1-AI62515 (Johns Hopkins) from the National Institute of Allergies and Infectious Diseases, NIH; and by the vaccine manufacturers Chiron Vaccines (formerly Biocine/Sclavo); Michigan Department of Public Health; Pasteur Mérieux Connaught (formerly Connaught, US, Pasteur-Mérieux, and Connaught, Canada); SmithKline Beecham Biologicals; Speywood Pharmaceuticals (formerly Porton Products); Swiss Serum Vaccine Institute; and Wyeth-Lederle (formerly Lederle-Praxis), whose products were evaluated.
John La Montagne, PhD, George Curlin, MD, David Klein, PhD, William Blackwelder, PhD, Martha Mattheis, MA, and George Reed, PhD, at the National Institute of Allergy and Infectious Diseases, NIH, provided substantial input to the design, coordination, or analysis of this study. We also thank the many participating primary care physicians, study nurses, and parents for their contributions.
- Received January 28, 1997.
- Accepted April 3, 1997.
Reprint requests to (M.E.P.) Department of Microbiology and Immunology, 601 Elmwood Ave, Box 672, Rochester, NY 14642.
Serologic assays were performed by Theresa Romani and Deborah Jansen (CBER), Sherry Passador (Rochester), and Kathy Holland (Vanderbilt). Freyja Lynn assisted in evaluation of serologic data from the three laboratories.
- DTaP =
- diphtheria and tetanus toxoids combined with acellular pertussis vaccine •
- DTwP =
- diphtheria and tetanus toxoids combined with whole-cell pertussis vaccine •
- PT =
- pertussis toxoid •
- FHA =
- filamentous hemagglutinin •
- PRN =
- pertactin •
- FIM =
- fimbriae •
- NIH =
- National Institutes of Health •
- VTEUs =
- Vaccine Treatment and Evaluation Units •
- WCL =
- DTwP vaccine manufactured by Lederle Laboratories •
- WCM =
- DTwP vaccine manufactured by Massachusetts Public Health Laboratories •
- CBER =
- Center for Biologics Evaluation and Research •
- EU =
- ELISA units •
- GMC =
- geometric mean concentration •
- CHO =
- Chinese hamster ovary •
- AGG =
- agglutinins •
- GMT =
- geometric mean titer
- Mortimer EA Jr.
- Edwards KM
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- Copyright © 1997 American Academy of Pediatrics