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The Rotavirus Vaccine's Withdrawal and Physicians' Trust in Vaccine Safety Mechanisms
Heather A. McPhillips, MD, MPH;
Robert L. Davis, MD, MPH;
Edgar K. Marcuse, MD, MPH;
James A. Taylor, MD
Arch Pediatr Adolesc Med. 2001;155:1051-1056.
ABSTRACT
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Objective To determine how the withdrawal from the market of the rotavirus vaccine
has affected physicians' trust in vaccine safety mechanisms, future adherence
to vaccine recommendations, and willingness to use a new rotavirus vaccine.
Design National survey mailed to 1228 randomly selected pediatricians and family
physicians.
Main Outcome Measures Confidence in vaccine safety mechanisms was defined by agreement with
the statements that the system for determining vaccine safety before a vaccine
is licensed works well and that the system for monitoring vaccine safety after
vaccine licensure works well. Physicians who indicated that they would use
a new rotavirus vaccine within 1 year of licensure and recommendation by professional
organizations were classified as "early adopters." Logistic regression was
used to assess the relationship between trust in vaccine safety mechanisms
and future early adoption of new rotavirus vaccines.
Results Following the withdrawal of the rotavirus vaccine, 83% of respondents
believed the postlicensure surveillance system works well to monitor vaccine
safety, while 22% of respondents believed the prelicensure system works well
to determine vaccine safety. After adjusting for physician specialty and years
in practice, respondents who believed the prelicensure vaccine safety system
works well were significantly more likely to be early adopters than those
with less confidence in prelicensure studies (adjusted odds ratio, 2.2 [95%
confidence interval, 1.3-3.6]).
Conclusions Physicians have different levels of trust in prelicensure studies that
determine vaccine safety and postlicensure surveillance systems that monitor
vaccine safety. Trust in prelicensure vaccine safety evaluations may be associated
with early adherence to new vaccine recommendations.
INTRODUCTION
THE PAST decade has seen an explosion of vaccine research and development.1 Vaccines against hepatitis B, varicella, rotavirus,
and pneumococcus have been added to the recommended childhood immunization
schedule.2 With the addition of these new vaccines,
some of which prevent diseases generally perceived as less serious (rotavirus,
varicella), and with the rarity of outbreaks from vaccine-preventable diseases,
more concerns are being raised in the popular press as well as the medical
literature about vaccine safety.3, 4, 5
The United States has several mechanisms to ensure that licensed vaccines
are safe for use in the general public. The first steps are the prelicensure
clinical studies, which are designed to determine the overall safety, immune
response, efficacy, and the risk of adverse effects from vaccines in the group
for whom the vaccine is intended.6, 7, 8
These studies are limited in their ability to detect very rare adverse events
because the studies are performed on 10 000 to 20 000 children.
After licensing by the Food and Drug Administration (FDA), Washington, DC,
vaccines are monitored for safety by the Vaccine Adverse Events Reporting
System, a passive surveillance system that receives case reports from providers
and parents of children who have adverse events temporally associated with
vaccination.9, 10 The Vaccine Adverse
Events Reporting System reports raise hypotheses that can be evaluated using
the Vaccine Safety Datalink, a database that collects clinical information
on 2% to 4% of the nation's children at 4 large West Coast health maintenance
organizations and allows for population-based assessment of vaccine safety.11 Special epidemiologic studies are conducted by federal
agencies in conjunction with states when postlicensure studies are inconclusive
or require confirmation.
The rapid withdrawal of the tetravalent rhesus-human reassortant rotavirus
vaccine (RotaShield; Wyeth Laboratories Inc, Marietta, Pa) only 11 months
after licensing may have affected providers' trust in future prelicensing
vaccine safety evaluations12, 13, 14
and may change the way providers make decisions regarding whether to adhere
to recommendations for new vaccines. Because of the potential cost savings
in the United States and the important impact on morbidity and mortality from
rotavirus diarrhea globally,12, 15
pharmaceutical companies are continuing to pursue development of both attenuated
human and bovine-human reassortant rotavirus vaccines.1
The potential risk of intussusception after immunization with these types
of rotavirus vaccines has not been established.8, 16
We conducted a national survey of pediatricians and family physicians
to determine how the withdrawal of the RotaShield vaccine has affected physicians'
trust in vaccine safety mechanisms, future adherence to vaccine recommendations,
and willingness to use a new rotavirus vaccine. We also wanted to determine
if any important differences exist between family physicians' and pediatricians'
confidence in vaccine safety or the likelihood of future utilization of new
vaccines.
SUBJECTS AND METHODS
SUBJECTS
We obtained a list of 614 pediatricians and 614 family physicians randomly
selected from the American Medical Association's Physician Masterfile of licensed
physicians in the United States. We limited our sample to currently practicing
pediatricians and family physicians living in the United States who completed
residency training in their specialty, were listed as general or primary care
physicians, and stated that their practice site was office- or hospital-based.
In addition to names and addresses, the database provided information on each
physician's age, sex, birthplace, medical school and year of graduation, residency
training and training dates, and practice specialty.
In February 2000, we sent each physician a questionnaire that required
approximately 10 minutes to complete and included return postage. A $1 bill
was included in the first mailing as an incentive to respond. Nonrespondents
received up to 3 additional questionnaires spaced approximately 1 month apart.
The final mailing was completed in June 2000. The University of Washington,
Seattle, institutional review board approved this study
SURVEY INSTRUMENT
The survey instrument had questions designed to determine (1) how confident
physicians are about the prelicensure studies in determining vaccine safety;
(2) how confident physicians are about the postlicensure surveillance system
to monitor vaccine safety; (3) whether a new rotavirus vaccine would be accepted
by physicians if the American Academy of Pediatrics (AAP), Advisory Committee
on Immunization Practices (Centers for Disease Control and Prevention) (ACIP),
and the American Academy of Family Physicians (AAFP) were to recommend the
new vaccine; (4) how soon after recommendations physicians would adopt a new
vaccine; and (5) the perceived importance of a rotavirus vaccine in the United
States. The survey instrument also contained questions on demographic information,
including physician practice location, practice type, number of children seen
per week, subspecialty training, patients' insurance status, and years since
completion of residency. Finally, the survey contained questions to determine
the physician's experience with rotavirus disease and the RotaShield vaccine.
OUTCOMES
Confidence in vaccine safety mechanisms following withdrawal of the
RotaShield vaccine was assessed by asking physicians if they believed the
current system for determining new vaccine safety before the FDA approves
a vaccine works well and whether the system for monitoring new vaccine safety
after a vaccine is approved by the FDA works well. For purposes of this analysis,
answers were dichotomized to "Yes" or "No/Undecided." Physicians were also
asked to agree or disagree with 4 statements assessing the effect of the RotaShield
vaccine withdrawal on physicians' trust in new vaccines and physicians' opinions
about the impact of the vaccine withdrawal on their patients' trust in vaccines.
Answers to this section were dichotomized to "strongly agree/agree" or "neutral/disagree/strongly
disagree."
We defined future "early adopters" of a new rotavirus vaccine as physicians
who said they would feel comfortable using a new rotavirus vaccine based on
FDA approval and AAP/ACIP/AAFP recommendation alone and would personally recommend
the vaccine within 1 year of its inclusion into the recommended immunization
schedule.
STATISTICAL ANALYSIS
Physicians who responded but were ineligible because they did not administer
vaccines to children were excluded from the analyses. The Pearson  2 test was used for categorical and dichotomous variables, and the Wilcoxon
rank-sum test was used to compare nonparametric means. A separate analysis
was performed using multiple logistic regression to determine what factors
were associated with future early adopters of a new rotavirus vaccine. Variables
were included in the final regression model if they were significantly associated
with early adoption on bivariate analysis, or were important confounding factors
or effect modifiers of the relationship between early adoption and confidence
in vaccine safety mechanisms. Stata version 6 computer software (Stata Corp,
College Station, Tex) was used for all analyses.
RESULTS
Of the 1228 surveys mailed, 49 were returned unopened with no forwarding
address (32 pediatricians and 17 family physicians). Of the 1179 physicians
contacted, 740 responded for an overall response rate of 63%. Among the 582
pediatricians contacted, 394 (68%) responded; 328 completed questionnaires,
while 66 responded that they did not provide immunizations to children. Five
hundred ninety-seven family physicians were contacted, and 346 (58%) responded;
230 completed questionnaires, and 116 responded that they did not provide
immunizations to children. The final sample size was 558 physicians.
Respondents stratified by specialty type did not differ significantly
from nonrespondents in any variable available to us in the address database,
including age, sex, type of practice, or country of birth. No significant
differences were observed in physicians who responded to the first, second,
or third mailing.
Characteristics of eligible respondents are summarized in Table 1. Forty-eight percent of physicians reported practicing in
a private group setting, and 26% reported practicing in solo private practice.
Pediatricians who responded had been practicing for slightly longer on average
than family physicians, were more likely to practice in an urban setting,
and reported seeing more children per week for preventive care.
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Table 1. Demographics of Survey Respondents by Specialty Type
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Eight to 12 months following the withdrawal of the RotaShield vaccine,
physicians expressed a high level of confidence in postlicensure vaccine surveillance
mechanisms but reported a low level of confidence in the effectiveness of
prelicensure studies to ensure vaccine safety (Table 2). Overall, 22% of physicians reported that the prelicensure
system works well, while 83% of physicians reported the postlicensure system
works well. Forty-three percent of respondents reported reluctance to use
any new rotavirus vaccine, while 28% of physicians reported that the withdrawal
of the RotaShield vaccine has made them more reluctant to use any new vaccine.
Nearly 40% of physicians felt their patients were more concerned about vaccine
safety than ever before, but only 30% of physicians felt that the withdrawal
of the RotaShield vaccine has increased distrust of new vaccines among their
patients.
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Table 2. Confidence in Safety Mechanisms and Effect of Rotavirus Vaccine
Withdrawal on Perceptions of Vaccine Safety*
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Physician attitudes regarding a new rotavirus vaccine are summarized
in Table 3. Only a slight majority
of respondents (57%) indicated that a rotavirus vaccine is needed. Once a
new rotavirus vaccine is recommended, 34% of physicians responded that they
would utilize the immunization within 6 months of the recommendation, while
64% would use it within 12 months. When asked what type of recommendation
would be needed to allow clinicians to feel comfortable using a new rotavirus
vaccine, the most common response was recommendation by organizations such
as the AAP, AAFP, and ACIP; widespread use of the immunization was the second
most common response. There were significant differences between pediatricians
and family physicians regarding attitudes about a new rotavirus vaccine. Pediatricians
were significantly more likely than family physicians to indicate that a new
vaccine is needed (63% vs 49%) and that they would use a new vaccine within
6 months (41% vs 23%).
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Table 3. How Important Is a New Rotavirus Vaccine for Use in the United
States and How Soon Would Physicians Use a New Vaccine Once Approved by the
FDA?*
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There were a number of physician characteristics and attitudes associated
with early adoption of a future rotavirus vaccine (Table 4). In the multivariate model, physicians who believed the
prelicensure system to ensure vaccine safety worked well were more than twice
as likely to meet criteria for a future early adopter of a rotavirus vaccine
than physicians who were undecided or did not believe the system worked well
(adjusted odds ratio [AOR], 2.2; 95% confidence interval [CI], 1.3-3.6). Conversely,
physicians who agreed with the statement "the withdrawal of the RotaShield
vaccine has made me more reluctant to use any new vaccine in the future" were
less than half as likely to meet criteria for a future early adopter (AOR,
0.4; 95% CI, 0.3-0.7). Pediatric specialty and completion of residency more
than 5 years ago were also more likely to be associated with early adoption
of a future rotavirus vaccine.
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Table 4. Responses Associated With Early Adoption of a New Rotavirus
Vaccine*
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Pediatricians consistently ranked the importance of vaccines higher
than family physicians for 5 vaccine-preventable infections (Figure 1). However, both groups of physicians ranked the measles
vaccine as most important, followed by vaccines against pertussis, pneumococcus,
varicella, rotavirus, and hepatitis A. Despite seeing significantly fewer
children for preventive care, family physicians did not differ significantly
from pediatricians in how likely they were to report having had a patient
experience a serious adverse event (self-defined by the physician) related
to a vaccine (18% vs 24%, P = .08 [2
test]). Pediatricians were significantly more likely than family physicians
to report recommending varicella vaccine to their patients all of the time
(80% vs 33%, P<.01 [2 test]).
Eleven percent of family physicians reported they never recommend varicella
vaccine to their eligible patients compared with 3% of pediatricians.
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Percentage of family physicians and pediatricians who responded that
a vaccine was very important for universal use in children for 6 vaccine-preventable
infections. The differences between specialty type for each vaccine-preventable
disease except hepatitis A was P<.01 (2 analysis).
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COMMENT
Results of this study indicate that physicians make an important distinction
between prelicensure studies to determine new vaccine safety and postlicensure
surveillance systems such as the Vaccine Adverse Events Reporting System and
Vaccine Safety Datalink that monitor vaccine safety. Following the withdrawal
of the rotavirus vaccine, trust in prelicensure studies was low, whereas trust
in the postlicensure surveillance system to monitor vaccine safety was high.
Furthermore, nearly half of physicians reported some reluctance to use a new
rotavirus vaccine if one is released, and more than one fourth of physicians
stated that the withdrawal of the RotaShield vaccine has increased their reluctance
to use other new vaccines. The observed difference in confidence between prelicensure
and postlicensure vaccine safety mechanisms in this study likely reflects
events surrounding the release and rapid withdrawal of the rotavirus vaccine.
While prelicensure studies did not detect a significant association between
the rotavirus vaccine and intussusception, postlicensure surveillance rapidly
detected a strong, statistically significant signal, and this information
was acted on quickly by federal agencies. If there had been a greater time
lag in detecting the increased risk of intussusception after vaccine licensure,
there may have been lower confidence in the postlicensure vaccine safety mechanisms.
This study does not allow any general conclusions about physician confidence
in prelicensure and postlicensure vaccine safety efforts with regard to other
vaccines.
The disparity in trust between prelicensure vaccine safety mechanisms
and postlicensure safety surveillance could potentially lead to continued
support by physicians for vaccines once in widespread use but reluctance to
adopt new vaccine recommendations. In our study, those physicians who would
use a new rotavirus vaccine within 1 year following a recommendation by professional
organizations were also twice as likely to trust in prelicensure vaccine safety
mechanisms. However, one third of respondents indicated they would not use
a rotavirus vaccine until it had been in widespread use for months to years.
Based on the results of our study, we do not know if the introduction of other
new recommended vaccines would face similar obstacles. Future studies could
attempt to determine why, given the same level of safety information, some
physicians trust in vaccine safety studies and are willing to rapidly adopt
new recommendations for vaccines, while other physicians have a "watch-and-wait"
attitude toward new vaccines.
Despite the association between RotaShield and intussusception and its
rapid withdrawal from the market, the majority of physicians believe we need
a vaccine against rotavirus; fewer than 2% of physicians responded they would
never use a rotavirus vaccine in children. In our survey, most physicians
reported they would wait longer than 6 months after recommendation by the
AAP/ACIP/AAFP before administering a new rotavirus vaccine to their patients.
If a new rotavirus vaccine is approved by the FDA and recommended by the AAP/ACIP/AAFP,
strong efforts will need to be made to assure physicians and parents that
adequate prelicensure studies were conducted to determine vaccine safety.
Prelicensure clinical evaluation of the rhesus-human reassortant vaccine
lasted longer than 15 years, cost hundreds of millions of dollars, involved
multiple agencies and investigators, and involved administration to more than
10 000 children.8 Careful retrospective
evaluation of the prelicensure data after the vaccine withdrawal determined
that the prelicensure studies did not reveal an association between the vaccine
and intussusception because the risk of intussusception was approximately
1 per 5000 vaccinated children, too rare to be identified in a trial of 10 000
children.8 Tremendous resources are needed
to conduct very large prelicensure trials, so a balance must be struck between
enrolling enough children in a randomized trial to determine the efficacy
and safety of a vaccine and the cost of vaccine trials, which translates into
the cost of the vaccine after licensure. Enrolling more children in prelicensure
vaccine studies to determine the risk of rare adverse events would not only
drive the cost of the vaccine up, potentially beyond affordability for universal
use in children, but also substantially delay the availability of the vaccine.
There were some important differences between family physicians and
pediatricians in this survey, consistent with other studies.17, 18, 19, 20, 21
Results from a recent national immunization survey indicated that children
(aged 19-35 months) who receive immunizations solely from family physicians
are significantly less likely to be up-to-date on their immunizations.22 We found that family physicians were less likely
to believe that a vaccine against rotavirus is needed and were less likely
to trust postlicensure vaccine safety mechanisms. Overall, family physicians
rated vaccines against 5 vaccine-preventable diseases as less important than
pediatricians did. Fewer than half of family physicians reported following
recommendations for universal varicella vaccination of children. Family physicians
did not differ significantly from pediatricians in reporting serious adverse
events associated with vaccines in their patients, despite seeing far fewer
pediatric patients for preventive care. This may reflect differences in their
confidence about vaccine safety, differences in the way they define a serious
adverse event associated with a vaccine, or differences in the incidence of
serious adverse events given different patient populations. Although family
physicians immunize considerably fewer children than pediatricians, approximately
23% of impoverished children receive their immunizations solely from family
medicine physicians.22 These same children
are at highest risk for poor outcomes from vaccine-preventable diseases.23, 24 Efforts are needed to determine why
family physicians have different attitudes and practices toward immunizations
than pediatricians. Family physicians may require additional or different
information than pediatricians in their decision-making process.
There are limitations to this study. Although we were able to determine
there was no significant difference in age, sex, or board certification, we
do not know if nonrespondents differed from respondents in any way that would
change our results. Nonresponse bias is an important limitation of mail surveys;
however, our response rate of 63% is in keeping with most other published
studies involving national surveys of physicians.25, 26
As found in previously published surveys on immunization practices,18, 19, 26 pediatricians had
a higher response rate than family physicians. The most plausible explanation
for this difference is the higher proportion of family physicians who do not
immunize children. Among our respondents, only 17% of pediatricians did not
immunize children compared with 34% of family physicians. Physicians who do
not immunize children are likely to have less incentive to return a survey
on immunizations. Another important limitation of this study is that it was
conducted within 10 months of the withdrawal of the RotaShield vaccine. It
is not known if the responses that physicians gave are consistent with what
their attitudes will be about new rotavirus vaccine recommendations and trust
in vaccine safety mechanisms after more time has passed.
Despite these limitations, our data strongly suggest that most physicians
believe that we need a safe and effective vaccine against rotavirus for use
in the United States. Physician trust in vaccine safety mechanisms is mixed.
There is skepticism about the ability of prelicensure studies to determine
vaccine safety; however, trust in postlicensure surveillance systems that
ensure vaccine safety is high. If physicians are able to trust prelicensure
studies to determine vaccine safety, they may be more likely to rapidly adopt
new vaccine recommendations. Future research could determine if these opinions
are stronger given the circumstances of the RotaShield vaccine withdrawal
or are consistent beliefs that will affect future new vaccine uptake of any
new rotavirus vaccine as well as any other new vaccines against childhood
illness.
AUTHOR INFORMATION
Accepted for publication April 10, 2001.
This study was funded by the Ambulatory Pediatric Association's Special
Project Grant for Immunization-Related Research, McLean, Va (Drs McPhillips,
Davis, and Taylor).
What This Study Adds
The rapid withdrawal from the market of the tetravalent rhesus-human
reassortant rotavirus vaccine (RotaShield) 11 months after FDA licensure may
have affected physicians' trust in vaccine safety evaluations. This study
was conducted to determine how the withdrawal of the rotavirus vaccine less
than 1 year after licensure (1) affected physicians' confidence in vaccine
safety mechanisms, (2) their willingness to use a new rotavirus vaccine if
one is approved, and (3) future likely adherence to new vaccine recommendations.
Following withdrawal of the rotavirus vaccine, there was a large disparity
in physician trust between prelicensure studies to determine vaccine safety
and the postlicensure surveillance system. Physicians who believed that the
prelicensure system to ensure vaccine safety worked well were more likely
to be future early adopters of a new rotavirus vaccine. Prelicensure safety
evaluations may be an important determinant in early adherence to new vaccine
recommendations.
From the Child Health Institute (Drs McPhillips, Davis, and Taylor),
the Department of Pediatrics, School of Medicine (Drs McPhillips, Davis, Marcuse,
and Taylor), and the Department of Epidemiology, School of Public Health and
Community Medicine (Drs Davis and Marcuse), University of Washington, and
the Children's Hospital and Regional Medical Center (Drs McPhillips and Marcuse),
Seattle.
Corresponding author and reprints: Heather McPhillips, MD, MPH, Department
of Pediatrics, University of Washington, 4800 Sand Point Way NE, PO Box 5371,
Mail stop CH-30, Seattle, WA 98105 (e-mail: hmcphil{at}u.washington.edu).
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ABSTRACT
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
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Jacobson et al.
CLIN PEDIATR 2008;47:500-503.
Who's Calling the Shots? Pediatricians' Adherence to the 2001-2003 Pneumococcal Conjugate Vaccine-Shortage Recommendations
Broder et al.
Pediatrics 2005;115:1479-1487.
ABSTRACT
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A Survey of Pediatricians on the Reintroduction of a Rotavirus Vaccine
Iwamoto et al.
Pediatrics 2003;112:e6-10.
ABSTRACT
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Withdrawal of rotavirus vaccine teaches industry importance of large trials
Wallace
AAP News 2002;20:15-16.
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