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Physician Attitudes Regarding Breakthrough Varicella Disease and a Potential Second Dose of Varicella Vaccine

^a Child Health Evaluation and Research Unit, Division of General Pediatrics
^b Division of General Internal Medicine
^c Gerald R. Ford School of Public Policy, University of Michigan, Ann Arbor, Michigan
^d National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia

	ABSTRACT

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
OBJECTIVE. We assessed physicians’ attitudes about the 1-dose varicella vaccination program and whether physicians think a 2-dose recommendation is needed to reduce the risk of breakthrough disease.

METHODS. We conducted a national mail survey of a random sample of 550 pediatricians and 550 family physicians from April to June 2005. Physicians who provide outpatient primary care to children 6 years of age were eligible for analysis.

RESULTS. Surveys were returned by 727 respondents, for a response rate of 69%; 610 physicians were eligible. Most respondents (94%) recommend routine 1-dose varicella vaccination, and 79% have seen breakthrough disease in the past 5 years (95% of pediatricians and 58% of family physicians). The majority (68%) agreed or strongly agreed that the current burden of breakthrough disease is acceptable. Only 38% (46% of pediatricians and 28% of family physicians) agreed or strongly agreed that a second dose of varicella vaccine is needed to address the burden of breakthrough disease, whereas 40% were neutral. However, if the Advisory Committee on Immunization Practices were to recommend a second dose of varicella vaccine, then 65% of pediatricians and 39% of family physicians would likely follow the recommendation. Most respondents (78%) would be more willing to recommend a second dose if a combination measles-mumps-rubella-varicella vaccine was available.

CONCLUSIONS. Pediatricians and family physicians support the 1-dose varicella vaccination program. A new Advisory Committee on Immunization Practices recommendation for a second dose of varicella vaccine for children was issued after the survey (in June 2006). Two of 3 pediatricians and 2 of 5 family physicians stated that they would adopt a 2-dose recommendation in practice; rates of adoption may be bolstered with current availability of measles-mumps-rubella-varicella vaccine and harmonization of the varicella vaccination schedule with that of measles-mumps-rubella vaccine.

Key Words: varicella • vaccine • physician • attitudes

Abbreviations: ACIP—Advisory Committee on Immunization Practices • FP—family physician • MMR—measles-mumps-rubella • MMRV—measles-mumps-rubella-varicella

Varicella vaccine was first licensed in the United States in 1995 and was recommended shortly thereafter for universal administration, as 1 dose, to children 12 to 18 months of age.^1,2 National immunization rates among toddlers were slow to increase but were boosted by many states’ day care and school entry requirements³ and reached 88% by 2004.⁴ Concurrently, rates of varicella illness decreased,⁵ as did varicella-related mortality rates⁶ and health care utilization rates, with consequent savings in health care spending.^7,8

Outbreaks of varicella continue to occur, however, and the number of reported cases of varicella has not changed substantially in the past 3 to 4 years. In recently published outbreak investigations, varicella vaccine effectiveness was typically between 70% and 90%.^9–15 Some outbreaks occurred among populations with high varicella vaccination coverage (>95%),^11,15,16 and all included cases of varicella in vaccinated persons (ie, "breakthrough" cases). Although breakthrough disease is usually milder than varicella in unvaccinated persons, breakthrough cases have played important roles in transmission of the disease.^11,15,16

The issue of breakthrough varicella has prompted questions of whether a second dose of varicella vaccine is needed.^{12,15,17–19} In clinical trials, a second dose yielded a small but statistically significant increase in estimated vaccine efficacy, from 94.4% to 98.3%.²⁰ The extent to which practicing physicians perceive breakthrough varicella as a burden is not known, however. Moreover, physicians’ perspectives regarding a potential recommendation for a second dose have not been examined. A related consideration is the availability of a measles-mumps-rubella-varicella (MMRV) combination vaccine, which may simplify administration of a second dose of varicella vaccine.

To address these gaps in understanding, we undertook a national survey of primary care pediatricians and family physicians (FPs), to characterize their attitudes regarding breakthrough varicella disease and a potential recommendation for a second dose of varicella vaccine. Preliminary data were provided to the US Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention in June 2005, to inform its initial deliberations regarding a possible recommendation for a second dose of varicella vaccine. After this study, MMRV vaccine was licensed by the Food and Drug Administration.²¹ In addition, the ACIP voted in June 2006 to recommend a second dose of varicella vaccine for all children 4 to 6 years of age.²² Findings from this study should help guide efforts to implement the second-dose varicella vaccine recommendation.

	METHODS

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Sample
We obtained a national random sample of pediatricians and FPs from the American Medical Association Masterfile, a database of all licensed US physicians, through a contracted vendor (Medical Marketing Service, Wood Dale, IL). The sampling frame included all allopathic and osteopathic physicians self-described as general pediatricians or FPs in office-based patient care; it excluded physicians 70 years of age, resident physicians, and physicians practicing at federally administered medical facilities (eg, Veterans Affairs or military facilities). The final mailing sample included 1100 physicians (550 pediatricians and 550 FPs). The study was approved by the institutional review board of the University of Michigan Medical School and was exempted from review by the institutional review board of the Centers for Disease Control and Prevention.

Survey Instrument and Administration
The study team developed a 2-page survey instrument with 13 closed-ended questions. On the basis of the clinical and public health experiences and immunization research expertise of the investigators, the survey items included current implementation of routine varicella vaccination, perceived success of the 1-dose vaccination program in reducing disease burden, experience with breakthrough varicella cases, extent of agreement with statements regarding breakthrough disease and a potential second dose of varicella vaccine, preferred scenario for timing of a potential second dose, perceived impact of a combination MMRV vaccine on acceptance of a second dose of varicella vaccine, and practice characteristics.

We also developed a 1-page "fact sheet" for survey recipients that summarized briefly the purpose of the study and presented information on the 1-dose varicella vaccination program, breakthrough varicella disease, estimated efficacy data from vaccine trials comparing 1-dose and 2-dose regimens of varicella vaccine, and the potential licensure of a MMRV vaccine. The survey questions and the fact sheet were pilot-tested with a convenience sample of primary care pediatricians and FPs, to ensure clarity and ease of administration, and refinements were made on the basis of pilot-test feedback.

Survey Administration
The initial mailing was sent in April 2005, and 2 subsequent mailings were sent to nonrespondents at 4-week intervals. The survey mailings included a personalized cover letter inviting participation, the fact sheet, and a postage-paid reply envelope; the first mailing also included a monetary incentive ($5).

Data Analysis
After verification of data entry, we generated univariate frequencies for each variable and conducted bivariate analyses by using a likelihood ratio ² test. P values of <.05 were considered significant. All analyses were conducted with SAS 8.2 (SAS Institute, Cary, NC).

	RESULTS

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Sample Characteristics
Of the 1100 physicians in the mailing sample, 52 (26 pediatricians and 26 FPs) were excluded because mailing materials were returned as undeliverable. Surveys were returned by 727 respondents (389 pediatricians and 338 FPs), for a response rate of 69% (74% for pediatricians and 65% for FPs). Of the 727 respondents, 117 (47 pediatricians and 70 FPs) were ineligible because they did not provide outpatient primary care for children 6 years of age, leaving 610 surveys (342 from pediatricians and 268 from FPs) available for analysis.

Of the 610 eligible respondents, the majority (53%) were male and almost all were board-certified in their respective specialty (89%). Most (70%) were in private practice, with another 10% in hospital-based outpatient care, 8% in practice networks or managed care organizations, and the remainder in other practice settings. A minority (18%) worked in solo practices, whereas 46% had 2 to 5 physicians in their practice and 36% had >5 physicians. More than one half (57%) enrolled >50 newborns in their practice annually, although this differed significantly according to specialty (88% for pediatricians and 17% for FPs; P .0001).

Perspectives on 1-Dose Varicella Vaccination Program
Most respondents (82%) "strongly recommend" routine 1-dose varicella vaccination for children 6 years of age in their practice, 12% "recommend" routine vaccination, and 6% ranged from "neutral" to "do not recommend." Pediatricians were significantly more likely than FPs to strongly recommend vaccination (93% vs 69%; P .0001) (Table 1). For 69% of respondents, the majority of children 6 years of age were vaccinated at the 12-month well-child visit, compared with well-child visits at 15 months or 18 months or later visits before school entry. The proportion administering the vaccine at the 12-month visit to the majority of children 6 years of age was greater for pediatricians (75%) than for FPs (60%; P .0001). A large proportion of respondents thought that routine 1-dose varicella vaccination has been successful in reducing the varicella disease burden, with some differences according to specialty (Table 1).

The majority of physicians (68%) agreed or strongly agreed that the burden of breakthrough disease is acceptable. Another 21% were neutral and 11% disagreed or strongly disagreed. The majority of physicians (71%) who had experienced breakthrough varicella agreed or strongly agreed that the burden of breakthrough disease is acceptable. There was no statistically significant difference in the level of agreement regarding the acceptability of breakthrough disease burden according to physician specialty (Table 2).

Perspectives on a Potential Recommendation for a Second Dose of Varicella Vaccine
Thirty-eight percent of respondents agreed or strongly agreed that a second dose of varicella vaccine is needed to address the burden of breakthrough disease, whereas 40% were neutral and 22% disagreed or strongly disagreed. Respondents who had seen breakthrough disease were more likely than those who had not to agree that a second dose is needed (41% vs 25%; P < .001).

A larger proportion of pediatricians than FPs agreed or strongly agreed that a second dose is needed (46% vs 28%; P .0001) (Table 2). Within specialty, the extent to which respondents agreed that a second dose is needed was not associated significantly with whether they had seen breakthrough cases.

When asked to consider a scenario in which the ACIP recommended a second dose of varicella vaccine, 53% of respondents agreed or strongly agreed that they would be likely to recommend a second dose of varicella vaccine to their patients; 27% were neutral and 20% disagreed or strongly disagreed. Pediatricians were more likely than FPs to predict that they would adhere to an ACIP recommendation for a second dose (65% vs 39%; P .0001) (Table 2).

The majority of respondents (66%) thought that parents would accept a second dose of varicella vaccine, with another 26% who were neutral and 8% who disagreed or strongly disagreed. Pediatricians were more likely than FPs to endorse this statement (72% vs 59%; P .01).

Respondents who thought that a second dose is needed were more likely than others to agree that they would adhere to an ACIP recommendation for a second dose of varicella vaccine and that parents would accept a second dose recommendation (Table 3). Among those who were neutral about the need for a second dose (Table 3), less than one half (39%) would agree or strongly agree with a second-dose recommendation from the ACIP, but nearly two thirds of the same physicians thought that parents would accept a second dose if it was recommended.

Influence of MMRV Vaccine Availability
Respondents were asked to consider their level of support for a second dose of varicella vaccine in a scenario in which the ACIP recommends a second dose and a combination MMRV vaccine is available, assuming that vaccine cost is not a barrier. Most respondents (76%) indicated that they would be more willing to recommend a second dose of varicella vaccine (compared with their earlier level of support) to their patients if a combination MMRV vaccine was available. Most (87%) also agreed that, if MMRV vaccine was available, then parents would be more likely to accept a second dose of varicella vaccine. Physician specialty was not associated with any difference in the proportions of respondents who indicated that MMRV vaccine availability would increase either their willingness to recommend a second dose of varicella vaccine or the likelihood that parents would accept a second dose.

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Results of this national survey indicate that pediatricians and FPs support the 1-dose varicella vaccination program and think it has been effective in reducing the burden of varicella disease among their own patients. A large proportion of respondents had experience with breakthrough varicella. The majority of respondents thought that the burden of breakthrough varicella is acceptable in clinical practice, and less than one half thought that a recommendation for a second dose is needed. However, a majority of pediatricians indicated that they would likely recommend a second dose if it was recommended by the ACIP, and both pediatricians and FPs said that they would be more willing to recommend a second dose if MMRV vaccine was available.

After this study, MMRV was licensed for use.²¹ In June 2006, the ACIP voted to recommend a universal 2-dose varicella vaccination program for children, with a schedule harmonized with that of the MMR vaccine.²² Our findings likely anticipate physicians’ early responses to these changes in immunization recommendations and administration options.

The large proportion of respondents with experience with breakthrough varicella indicates that many physicians are aware that the 1-dose regimen of varicella vaccine does not always prevent varicella disease. Notably, the majority of physicians with experience with breakthrough disease thought that the breakthrough disease burden is acceptable, and less than one half of physicians with breakthrough experience reported that parents are upset about breakthrough disease. Consistent with these opinions about breakthrough varicella, less than one half of the physicians we surveyed thought that a recommendation for a second dose of varicella vaccine is needed to address the burden of breakthrough disease. This finding likely reflects a high level of satisfaction among physicians with 1-dose varicella vaccination efforts and associated decreases in varicella-related morbidity, death, and health care expenditures.^5–8

Physicians may not perceive breakthrough varicella they see in their practice as a major threat to children’s health and community health and therefore do not see a need to enhance its control. Breakthrough varicella cases are usually mild; however, studies indicate that 20% to 30% of such cases are as clinically severe as cases in unvaccinated persons.^{10,14,15,20,23} It may be helpful to provide more data on breakthrough varicella to clinicians as they consider implementing the second-dose recommendation.

Importantly, 2 of 5 physicians in this study had a neutral opinion regarding the need for a second dose and 1 of 4 were neutral regarding the likelihood that they would recommend a second dose if the ACIP recommended it. Given the subsequent ACIP recommendation for a second dose, it is unclear whether ambivalent physicians will adopt the recommendation and how other stakeholders (eg, other recommending organizations, vaccine companies, health plans, parents, and groups opposing vaccination) may influence their decisions.

When asked to consider a potential ACIP 2-dose recommendation, a majority (65%) of pediatricians anticipated that they would follow such a recommendation. This proportion is at the upper limits of a range of 42% to 63% of pediatricians who followed the 1-dose varicella recommendation in the first few years after implementation.^24–26 Of FPs, 39% predicted that they would likely recommend a second dose if ACIP recommends it, similar to the experience with initial FP acceptance of the first dose recommendation.^24,26 These specialty differences reflect patterns observed for other childhood vaccines recommended for universal administration to children within the past 2 decades.^27–29 The fact that a larger proportion of respondents predicted that they would be likely to recommend a second dose, compared with the proportion of respondents who thought that a second dose is needed, likely indicates that these physicians are willing to follow national guidelines of public health and professional organizations proposed after review of the evidence by those groups, rather than relying solely on their own clinical experiences.

The prospect of a combination MMRV vaccine led three fourths of both pediatricians and FPs to be more willing to recommend a second dose of varicella vaccine. We did not remeasure respondents’ anticipated adherence to a recommendation for a second dose of varicella vaccine under the assumption of MMRV availability; therefore, we cannot say precisely whether being more willing to recommend translates into being likely to recommend a second dose. A majority (54%) of those more willing to recommend had already said that they would be likely to recommend a second dose.

This study focused on providers’ perception of varicella and its morbidity, as well as their perspectives on a potential second dose, given the vital role that primary care providers play in ensuring that their patient populations receive the recommended vaccines for children.³⁰ However, acceptance of the second dose also will be influenced by the perspectives of other stakeholders, including parents, public health officials, and payers.

For example, parents’ interest in a 2-dose varicella vaccination regimen may be prompted by concerns regarding breakthrough disease and time lost from work or school but tempered by concerns such as cost or a possible increase in the number of vaccine injections. Physicians in this study, particularly pediatricians, indicated that they thought parents would likely accept a 2-dose recommendation, although less than one half of all respondents thought that parents are upset about cases of breakthrough varicella.

From the public health perspective, support for recommendation of a second dose stems from the potential for transmission of varicella zoster virus via breakthrough cases.²³ The breakthrough rate, even in highly vaccinated populations, is sufficient to enable ongoing transmission of the virus, which can lead to severe disease among susceptible persons at high risk for complications or can sustain outbreaks.^11,15,31 Also, responding to an outbreak can be an expensive and personnel-intensive endeavor, even for diseases with high community vaccination levels, such as varicella and measles.³²

Opinions of payers, both private and public, regarding a second dose of varicella vaccine are not yet known. Important economic benefits of varicella vaccination to payers through decreased health care utilization have been identified in both ambulatory and inpatient care settings,^7,8 and cost-effectiveness analyses found the 1-dose vaccination program to be cost-saving³³ (F. Zhou, PhD, written communication, 2005). It is anticipated that a routine 2-dose program will further decrease varicella-related health care utilization, although the magnitude is uncertain.

Response bias is the chief limitation in studies using mailed surveys. Physicians who responded to the survey may be more interested in vaccination issues; it also may be that physicians who did not respond do not endorse childhood immunizations as actively. Although the potential for response bias exists, it is impossible to detect its direction. Our overall response rate is generally comparable to those of other published studies of physician behavior.^34–36

	CONCLUSIONS

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The results of this national survey suggest that children’s physicians are satisfied with the accomplishments of the current 1-dose varicella vaccination program. Now that the ACIP has recommended a second dose of varicella vaccine for children, this study indicates that 2 of 3 pediatricians and 2 of 5 FPs are likely to follow the recommendation. The current availability of MMRV vaccine and harmonization of the varicella and MMR vaccination schedules may yield higher levels of support for the 2-dose varicella vaccine regimen. However, ambivalence expressed by some providers, especially FPs, about the clinical need for a 2-dose varicella vaccine series may be an obstacle to early adoption of this new recommendation.

	ACKNOWLEDGMENTS

 
This work was funded by the Centers for Disease Control and Prevention.

	FOOTNOTES

 
Accepted Sep 28, 2006.

Address correspondence to Matthew M. Davis, MD, MAPP, University of Michigan, 300 N Ingalls, Room 6C23, Ann Arbor, MI 48109-0456. E-mail: mattdav{at}med.umich.edu

Dr Marin and Ms Cowan made equal contributions to the study and the manuscript.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the funding agency.

The authors have indicated they have no financial relationships relevant to this article to disclose.

	REFERENCES

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

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This Article Abstract Full Text (PDF) P3Rs: Submit a response Alert me when this article is cited Alert me when P3Rs are posted Alert me if a correction is posted Citation Map Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Davis, M. M. Articles by Clark, S. J. Search for Related Content PubMed PubMed Citation Articles by Davis, M. M. Articles by Clark, S. J. Related Collections Infectious Disease & Immunity

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