PEDIATRICS Vol. 108 No. 1 July 2001, pp. 123-128

Safety and Immunogenicity of a Recombinant Borrelia burgdorferi Outer Surface Protein A Vaccine Against Lyme Disease in Healthy Children and Adolescents: A Randomized Controlled Trial

Vijay K. Sikand, MD^*, Neal Halsey, MD, Peter J. Krause, MD^§, Sunil K. Sood, MD, Richard Geller, MD^¶, Christian Van Hoecke, MD^#, Charles Buscarino, BSc^**, Dennis Parenti, MD^**, and for the Pediatric Lyme Vaccine Study Group^a

From the ^* Division of Rheumatology/Immunology, Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts;  Department of International Health, Johns Hopkins University School of Public Health, Baltimore, Maryland; ^§ Department of Pediatrics, Connecticut Children's Medical Center, Hartford, Connecticut;  Division of Infectious Diseases, Long Island Jewish Health System-Children's Health Network of North Shore, New Hyde Park, New York; ^¶ Norwich Pediatric Group, Norwich, Connecticut; ^# SmithKline Beecham Biologicals, Rixensart, Belgium; and ^** SmithKline Beecham Biologicals, Collegeville, Pennsylvania.

	ABSTRACT

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Objective.  A recombinant lipoprotein outer surface protein A (OspA) Lyme disease (LD) vaccine (LYMErix) has been shown to be safe and effective in preventing LD in adults and in adolescents 15 years of age and older. Children are at risk for developing LD. This clinical study was conducted to address the safety and immunogenicity of LD vaccine in children 4 to 18 years of age.

Methods.  A randomized, placebo-controlled clinical trial was conducted at 17 investigational sites in Lyme-endemic areas in the United States. Immunogenicity data from this study also were compared with data obtained from the adult efficacy study. A total of 4090 healthy children and adolescents (age range: 4-18; mean age: 10.4 years) were randomized; 4087 were vaccinated, and a subset of 301 children participated in the immunogenicity analysis. Children were randomized to receive either 30 µg of LD vaccine (N = 3063) or placebo (N = 1024) on a 0, 1, 12-month schedule. Safety assessments evaluated both solicited (local: redness, swelling, and pain; general: fever, headache, fatigue, arthralgia, and rash) and unsolicited adverse events. Serum specimens were collected at month 0 or month 2, and months 6, 12, and 13.

Results.  Solicited reactogenicity data revealed a higher incidence of local injection site reactions and general symptoms (fever, headache, fatigue, and arthralgia) in vaccine than placebo recipients. The majority of events were limited in duration (mean: 2-3 days) and were mild to moderate in severity. The total IgG anti-OspA geometric mean titer (GMT) in the pediatric vaccine recipients at month 13 was as good as and statistically higher than the GMT in the adult cohort at month 13 (27 485 enzyme-linked immunosorbent assay units [EL.U]/mL vs 8216 EL.U /mL). All of the pediatric vaccine recipients attained a level of antibody concentration 1400 EL.U/mL (proposed seroprotective level) compared with 90% of adults attaining levels 1400 EL.U/mL in the efficacy trial.

Conclusions.  LD vaccine administered on a 0, 1, 12-month schedule generally is well tolerated and immunogenic in children 4 to 18 years of age. The safety profile consists of mild to moderate local injection site reactions and flu-like symptoms of limited duration and did not worsen with subsequent injections. IgG GMT at month 13 was threefold higher than the month 13 GMT obtained in the adult efficacy study. This higher immune response in children should provide protection against LD.  Key words:  vaccine, OspA, Lyme disease, pediatric, prevention.

Lyme disease (LD) is the most common vector-borne disease in the United States, accounting for >95% of all reported cases of vector-borne illness. LD, caused by infection with Borrelia burgdorferi, has increased approximately 25-fold since the Centers for Disease Control and Prevention began surveillance in 1982, with a mean of 12 451 cases reported each year between 1993 and 1997.¹ In addition, according to 2 reports,^2,3 the disease may be underreported by as much as 12-fold. The highest incidence of LD occurs in children who are younger than 15 years and in adults who are 30 to 59 years old. In recent years, children younger than the 15 years have composed nearly 30% to 40% of all reported cases in the United States.^4,5

The Food and Drug Administration has licensed a recombinant LD vaccine containing 30 µg of recombinant B burgdorferi lipidized outer-surface protein A (OspA; LYMErix; SmithKline Beecham Pharmaceuticals, Philadelphia, PA) for use in the United States in persons 15 to 70 years old. A randomized, controlled trial in the United States demonstrated that this vaccine was safe and prevented 76% of definite (laboratory-confirmed) symptomatic cases of LD and 100% of asymptomatic infections after 3 doses.⁶ The Advisory Committee on Immunization Practices recommends that vaccination be considered for persons who are 15 to 70 years of age and who engage in activities that result in exposure to a tick-infested habitat.⁷ A preliminary European trial of Lyme vaccine in 250 children who were 5 to 15 years of age demonstrated that the vaccine was well tolerated and that 30 µg was more immunogenic than 15 µg.⁸ To define further the safety and immunogenicity of LD vaccine in children, we conducted a controlled clinical trial in healthy children and adolescents 4 to 18 years of age.

	METHODS

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Study Population

A total of 4090 healthy children and adolescents were enrolled from 17 sites in LD-endemic areas in the United States. Participants were categorized into 3 age groups: 4 through 8, 9 through 13, and 14 through 18 years. For the immunogenicity subset, 301 participants (227 vaccine and 74 placebo recipients) were enrolled from 3 sites. The study began in April 1998, and the last safety data were collected in September 1999. Written, informed consent was obtained from each participant and/or his or her parent or guardian before study entry. The institutional review boards and independent ethics committees of all of the investigational sites approved the study.

Participants were excluded if they had 1) received Lyme vaccine; 2) a physician-diagnosed chronic illness related to LD; 3) active LD; 4) a current disease associated with joint swelling, diffuse joint or muscular pain, or unstable neurologic condition; 5) LD treated with antibiotic therapy within 1 month before enrollment; 6) second/third-degree atrioventricular block or a cardiac pacemaker; or 7) suspected or known of having immune dysfunction or major congenital defects.

Vaccine and Placebo Preparations

The vaccine contained 30 µg of purified recombinant lipoprotein OspA, expressed in Escherichia coli and adsorbed to 0.5 mg of aluminum hydroxide in phosphate-buffered saline, as reported by Van Hoecke et al⁹ and 2-phenoxyethanol as a preservative. The placebo was supplied in an identical manner to the vaccine, except for the absence of the lipoprotein-OspA antigen.

Study Design

In a multicenter, double-blind, placebo-controlled study, participants were randomized to receive vaccine (V) or placebo (P) in a 3:1 ratio. Vaccine and placebo were administered intramuscularly on a 0, 1, 12-month schedule. During the course of the study, LYMErix was approved by the Food and Drug Administration in December 1998 for use in individuals age 15 or older in the United States. Therefore, the protocol was amended to allow all participants who were 15 years or older to receive vaccine instead of placebo at the 12-month visit. This left all participants blinded for the first 12 months of the study. Starting at month 12, there were 4 groups: blinded vaccine (VB) and blinded placebo (PB) recipients, who were 4 to 14 years old, and unblinded vaccine (VU) and unblinded placebo (PU) recipients, who were 15 years or older. The PU recipients crossed over to receive open-label vaccine on a 0, 1, 12-month schedule after the month 13 visit. All vaccine recipients received their third dose of study vaccine and continued in the study for long-term safety evaluation. Figure 1 illustrates the relationship between groups and the number of participants within each group.

View larger version (19K): [in this window] [in a new window]   Fig. 1.   Randomized controlled trial flow diagram of study groups.

Assessment of Safety and Reactogenicity

All participants were monitored for adverse experiences (AEs) on days 0, 1, 2, and 3 with the use of diary cards. Safety postcards were given to parents/participants to record the occurrence of any unsolicited AE within 30 days of each dose after day 4. AEs also were recorded at the month 12 visit. Participants were asked about any new medical conditions, any swollen and/or painful joints, any visits to a rheumatologist or neurologist, or visits to any other specialists since their last visit. Serious AEs (hospitalization or significant hazard as determined by the investigator) were recorded throughout the study.

Solicited AEs included redness, swelling, and pain/soreness. General AEs included fever, headache, fatigue, arthralgia, and rash. Severity was defined on a scale of grades 0 to 3 as follows: grade 0, no AE; grade 1, easily tolerated, minimal discomfort, and no interference with daily activities; grade 2, sufficiently discomforting to interfere with daily activities; and grade 3, prevention of daily activities or school attendance or causing parents to seek medical advice. Fever was defined as follows: grade 1 (mild), 99.5°F to 100.4°F; grade 2 (moderate), 100.5°F to 102.2°F; and grade 3 (severe), greater than 102.2°F. Erythema or induration at the injection site <1 mm was scored as grade 0; grade 1 was 1 to 30 mm in diameter; grade 2 was >30 mm diameter; and grade 3 was >30 mm and persisting >24 hours.

Assessment of Immunogenicity

Serum for anti-OspA antibodies was obtained at months 2, 6, 12, and 13 at 2 study sites and at months 0, 2, 12, and 13 at a third site. In addition, serum samples from the adult trial were retested in serial assays with the pediatric samples at the same time. Sera for anti-OspA IgG were assayed by enzyme-linked immunosorbent assay (ELISA) by SmithKline Beecham Biologicals (Rixensart, Belgium). The IgG anti-OspA titers were expressed in arbitrary ELISA units (EL.U)/mL with an assay cutoff of 20 EL.U/mL. Seropositivity was defined as >20 EL.U/mL.⁹ Seroprotection was defined as having an IgG anti-OspA titer of 1400 EL.U/mL 1 month after the third injection; this concentration has been shown to provide protection against disease for at least the following season.^10,11 Geometric mean titers (GMTs) were determined by log-transformation of individual titers and use of the anti-log of the mean of transformed values for seropositive participants.¹²

Statistical Methodology

The primary endpoint for safety/reactogenicity was the occurrence of unsolicited AEs within 30 days of each vaccination for all symptoms classified by the World Health Organization Dictionary for Adverse Reaction Terminology.¹³ The occurrence of early unsolicited symptoms within 30 days after vaccination in the intention-to-treat cohort included participants in groups V and P for doses 1 and 2 and groups VB, VU, and PB for analyses involving dose 3. A sample size of 2875 evaluable participants (randomized 3:1) was needed to observe at least 1 occurrence of any unsolicited AE in the vaccine group with an incidence rate of 0.1% or greater.

The primary endpoint for the immunogenicity study was the measurement of total IgG anti-OspA antibodies at month 13 (1 month after dose 3) from children in group VB and at month 13 in sera reassayed from participants in the adult efficacy trial. A comparison of GMTs was made using the "as good or better approach." A 1-sided test for noninferiority was used, and data from the according-to-protocol (ATP) cohorts of both studies were used for the analysis. The ATP cohort was composed of participants who received the first 2 doses of study vaccine without a major protocol violation.

Study Assignment and Blinding

Participants who met enrollment criteria were centrally randomized with the use of a sponsor-derived, computer-generated randomization of participant identification numbers. Investigators were not given the randomization list. Remote data entry was used for data collection at each investigational site. Only authorized individuals could enter or modify data to ensure accuracy with source documents. Every precaution was taken to ensure that all procedures (data collection, data entry, and resolution of data discrepancies) were conducted in a blinded manner.

	RESULTS

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Demographics

A total of 4090 participants, ages 4 through 18 years, were randomized, 3065 in group V and 1025 in group P. Three participants withdrew after consent was obtained but before the first dose of vaccine was given. The intention-to-treat cohort for the safety analysis included 4087 participants (3063 in group V and 1024 in group P) who received at least 1 dose of vaccine or placebo. The mean age was 10.4 years: 35.5% were 4 to 8 years, 39.0% were 9 to 13 years, and 25.5% were 14 to 18 years. Fifty-four percent were male, and the majority of participants (96.5%) were white. An analysis of variance 2-way test demonstrated no statistically significant differences between vaccine or placebo groups for age or gender.

More than 95% of the participants completed the study, defined as returning for the month 12 study visit. There was no significant difference between the dropout rates (4.5% vs 4.6%) in groups V and P, respectively (P = .945). The most common reasons for participants' discontinuing the study were consent withdrawal, lost to follow-up, or moving from the area. A total of 256 participants (189 in group V and 67 in group P) composed the ATP cohort for the immunogenicity analysis. The demographics of participants in the immunogenicity subset were similar to demographics for all participants.

Safety and Reactogenicity Analysis

Tables 1 and 2 present solicited symptoms in blinded vaccine and placebo recipients ages 4 to 14 years (groups VB and groups PB) by dose and severity of symptoms. Overall, there were more local (78.2% and 55.1%) than general symptoms (30.1% and 21.5%) reported for both groups (Table 1). The percentage of symptoms decreased from the first dose (86.1% vs 68.2%) to second dose (74.2% vs 56%), respectively, for both groups (P < .001). There was a slight increase in symptoms after dose 3 (80.2% vs 74.2%), although the percentage remained less than that reported after the first dose (Table 2). The rates of local symptoms (pain, redness, and swelling) after each dose were significantly higher (P < .001) in vaccine than in placebo recipients. Also, headache, fatigue, and fever occurred consistently more frequently (statistically significant) in vaccine than in placebo recipients. The mean duration for these local and general solicited events was 2 to 3 days after each of the 3 doses and >97% resolved within the 4-day diary card observation period and did not worsen with subsequent injections.

Approximately 12% (N = 8992) of all LD vaccine doses and 17% (N = 2776) of placebo doses were followed by unsolicited symptoms; the overall rates of AEs were similar, and the incidence differences between the blinded vaccine and placebo groups were 0.6% for all AEs (classified by World Health Organization preferred terms). Injection site reactions were reported more frequently by the vaccine recipients, and rash was reported more frequently by placebo recipients.

Investigators also solicited information regarding any rheumatologic or neurologic AEs. Most of the neurologic events were attention deficit disorder or headache unrelated to study vaccine. The majority of the rheumatic complaints were attributed to trauma, chondromalacia, or Osgood-Schlatter disease. One vaccine recipient had transient ankle swelling after dose 2, which resolved and did not recur after dose 3. A second vaccine recipient received a diagnosis of Raynaud's syndrome, and a third vaccine recipient developed unilateral knee swelling attributed to mechanical stress.

Seven vaccine recipients (with chills and pain, chills, shaking, rigors, entire body aching, urticaria, and a prolonged local reaction) and 1 placebo recipient (with urticaria) withdrew from the study as a result of study-related AEs. Of the serious AEs reported (sarcoma of the left humerus, headache and vomiting, uncontrollable shaking, dysplasia, seizure, rigors, and drowning), only 2, rigors and shaking (in vaccine recipients), were reported as "probably related" to vaccination. There was no significant difference between the groups of AEs leading to dropout in vaccine versus placebo recipients (P = .415).

Immunogenicity Analysis

The serologic responses for the blinded and unblinded subsets of the vaccine recipients (groups VB and VU) in the ATP cohorts are shown in Table 3. Only 1 participant was positive at baseline for IgG anti-OspA antibodies. At month 2, 1 month after the second injection, all vaccine recipients were seropositive and 88.4% had GMTs 1400 EL.U/mL. At month 13, 1 month after the third dose, the GMT increased fivefold compared with month 2, and 100% had seroprotective titers.

Participants who were 14 to 18 years old at the time of enrollment attained a slightly lower GMT than participants who were 4 to 8 years or 9 to 13 years old. At month 2, 78% of vaccine recipients who were 14 to 18 years old had seroprotective levels compared with 93.9% of 4- to 8-year-old vaccine recipients and 89% of 9- to 13-year-old vaccine recipients. There were no age group differences in the rates of seroprotection at month 13.

The antibody response in children was superior to the antibody response observed in adults (Fig 2 and Table 4). The GMT from group VB at month 13 (29 650; 95% confidence interval [CI]: 25 707, 34 197) was significantly higher than the GMT from the adult efficacy trial (8217; 95% CI: 7084, 9530) with a relative difference of 2.61 (P < .001), with the use of a 1-sided test for noninferiority. Similarly, the GMT from the entire vaccine group (group V) at month 13 was significantly higher than the GMT from the adult efficacy trial (27 484.5; 95% CI: 24 141, 31291) with a relative difference of 2.35 (P < .001).

View larger version (18K): [in this window] [in a new window]   Fig. 2.   Reverse cumulative curves for total IgG anti-OspA antibody titers (EL.U/mL) at 2 and 13 months for the pediatric group VB (4 to 14 years) and for adults at month 13 in the adult efficacy trial.

All adolescent vaccine recipients (group V) were seroprotected at month 13 (100%), which was significantly higher (P = .001) than the 91.9% seroprotection rate at month 13 in the adult cohort. The seroprotection rate at month 2 in the pediatric cohort (91.3%) was not statistically different from the 91.9% seroprotection rate at month 13 in the adults (difference: 0.6; 95% CI: 6.2, 5.0; P = .838).

	DISCUSSION

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Recombinant OspA vaccine administered on a 0, 1, 12-month schedule was immunogenic and generally well tolerated in children and adolescents who were 4 to 18 years old. Vaccine administration was associated with symptoms at the site of injection and mild to moderate systemic reactions, including fever, fatigue, headache, and arthralgias with a mean duration of 2 to 3 days that did not worsen with subsequent injections. These data also are consistent with data from the adult efficacy trial in which 63% of vaccine recipients recorded related or possibly related early systemic symptoms versus 53% of placebo recipients.⁶

Seventeen percent of blinded vaccine recipients in this trial reported grade 3 injection-site soreness during the 4-day diary card observation period. In the adult trial, only 5% reported injection-site soreness of grade 3 severity. The protocol defined grade 3 intensity as preventing normal everyday activities, including school or child care center attendance or causing parents to seek medical advice. However, the written instructions on the diary cards defined grade 3 as "locally painful when the limb is moved/spontaneously painful (prevents normal activity)." This divergence confounded the classification of moderate and severe intensity, and we believe that 17% may overestimate the actual percentage of children who experienced severe soreness after vaccination.

In a post hoc informal review of the investigators, the most common reasons given for assessing local soreness as grade 3 were that the soreness interfered with sports or playing computer games. No investigators recalled requests by parents for medical attention or missed school days solely as a result of local soreness. Only 7 (0.2%) of 3063 vaccine recipients and 1 (0.1%) of 1024 placebo recipients withdrew from the study because of AEs that were considered related to vaccination by the investigators, and >95% of vaccine recipients received all 3 injections.

The possibility that OspA from the spirochete B burgdorferi might be associated with autoimmune arthritis in genetically predisposed individuals as a result of natural infection has been hypothesized by Gross et al.¹⁴ However, there was no evidence of increased risk of arthritis in adults who received recombinant OspA LD vaccine in the efficacy trials.^6,15 In this study, investigators actively solicited data regarding rheumatologic events after each injection and in safety postcard follow-ups. There was no increase in reports of arthritis in vaccine versus placebo recipients, and no one in this trial developed vaccine-related inflammatory arthritis. Children did not experience any pattern of clinical events suggestive of inflammatory arthritis despite the development of much higher IgG titers of OspA antibody as compared with adults. The mechanism of antibiotic treatment-resistant Lyme arthritis remains unclear and evidently involves a constellation of individual immunologic and microbiologic factors that probably are more related to natural infection by the organism than to exposure to OspA itself.

The greater immune response to LD vaccine in children as compared with adults is likely to be associated with improved protection after 2 doses because anti-OspA antibody titers are related directly to efficacy. The mechanism of action of this vaccine involves antibody-mediated borrelicidal activity in the midgut of the tick, where B burgdorferi primarily expresses OspA.¹⁶ In the adult trial, a total IgG anti-OspA serum concentration of  1400 EL.U/mL was associated with protection against LD.^10,11

In this study, 100% of vaccine recipients attained a seroprotective level 1400 EL.U/mL after 3 doses. Ninety-one percent of participants in the 4- to 14-year-old group attained seroprotective levels after the second dose. Therefore, a 2-dose primary vaccination schedule may be possible in this age group.

Long-term follow-up of adult study participants suggests that booster doses will be needed to maintain persistent immunity. Safety and immunogenicity of booster doses of the LD vaccine in adults have been reported. Administration of booster doses resulted in an anamnestic response and did not affect the safety or reactogenicity of the vaccine.^17,18 A multicenter study of the safety, immunogenicity, and reactogenicity of booster doses in children is being conducted in the original vaccine recipients who participated in the trial reported here.

In summary, the results of this study demonstrate that the recombinant OspA vaccine is safe and immunogenic in the 4- to 18-year-old pediatric and adolescent age group. Local and systemic side effects were similar to those in adults and generally were well tolerated; >95% of the vaccine recipients received all 3 injections. The immune response was substantially more robust in children compared with adults. Thus, this vaccine has the potential to contribute significantly to the prevention of LD in children, in addition to personal protective measures, early diagnosis, and appropriate antibiotic treatment.

	ACKNOWLEDGMENTS

This study was funded by SmithKline Beecham plc, a division of GlaxoSmithKline, plc; in addition to research grant support.

The primary investigators of the Pediatric Lyme Vaccine Study Group were (by order of site number) as follows: Neal Halsey, MD; Richard Geller, MD, Peter Krause, MD; Vijay K. Sikand, MD; Sharon Nachman, MD; Alan G. Kelsey, MD; Bradley J. Sullivan, MD; Jose Munoz, MD; Marc Tack, MD; Edward P. Rothstein, MD; Pauline B. Wood, MD; Sunil Sood, MD; Michael C. Caldwell, MD; Cody Meissner, MD; Kenneth Bromberg, MD; Henry M. Feder, MD; Todd A. Mahr, MD; Brian Allen, MD; Joel Klein, MD; Stephen Eppes, MD; and Linda Lewis, MD.

We thank the members of the Independent Data Safety Monitoring Board for monitoring the overall conduct of the study: Daniel W. Rahn, MD (Chairman; Medical College of Georgia, Augusta, GA); David P. Greenberg, MD (Children's Hospital of Pittsburgh, Pittsburgh, PA); Ned Hayes, MD (Centers for Disease Control and Prevention, Atlanta, GA); Margaret Rennels, MD (University of Maryland, College Park, MD); and Mark Wolff, PhD (Potomac, MD).

In addition, we thank Elke Sennewald, PhD (Kendle/GMI, Munich, Germany), for statistical analysis; and Esthner Chernak, MD (Philadelphia, PA), for editorial assistance.

	FOOTNOTES

^a Members of the Pediatric Lyme Vaccine Study Group are listed in "Acknowledgments."

Dr Sikand has served as a consultant and member of the Speakers Bureau for SmithKline Beecham. Dr Sood has served as a consultant to and has received honoraria from SmithKline Beecham Biologicals for lectures.

Dr. Parenti is currently at Wyeth-Ayerst Laboratories (St Davids, PA).

Received for publication Aug 11, 2000; accepted Nov 2, 2000.

Reprint requests to (V.K.S.) Box 610, East Lyme, CT 06333-0610.

	ABBREVIATIONS

LD, Lyme disease; OspA, outer surface protein A; AE, adverse experience; ATP, according-to-protocol; ELISA, enzyme-linked immunosorbent assay; EL.U, ELISA units; GMT, geometric mean titer.

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