Apr. 7, 2008 News stories about an allegedly harmful link between the mumps, measles and rubella vaccine and the onset of autism had little effect on whether U.S. parents immunized their children, according to a review of immunization records and news stories. Parents' decisions were more likely influenced by recommendations from their child's pediatrician, the researchers said.
Researchers from The Children's Hospital of Philadelphia and The University of Louisville School of Medicine report on the review of data in the April issue of the journal Pediatrics. The data was collected from public-use files of the National Immunization Survey from 1995 to 2004. It compared immunization records of 215,643 children ages 19 months to 35 months with spikes in news stories about the MMR vaccine and autism. The news accounts were gathered from a database known as LexisNexis, which tracks newspaper, television and radio news.
The number of children not receiving the mumps, measles and rubella vaccine (known as MMR) increased after February 1998, when a scientific study proposing a link between the MMR vaccine and autism appeared in the British journal The Lancet. After two years, the U.S. numbers of unvaccinated children then declined and did not rebound when the MMR-autism link started to receive widespread coverage in the mainstream press, suggesting a limited influence of news media on MMR immunization rates in the U.S.
"If providers become more cautious during a period of controversy, then public health officials should insure providers are given timely advisories and access to credible recommendations," said Michael J. Smith, M.D, lead author of the study while formerly at Children's Hospital. Smith is now a pediatric infectious disease specialist at the University of Louisville School of Medicine. "Our findings suggest that physicians may have been an important buffer against the potential negative impact of media coverage of immunization controversies."
The Lancet study, led by Andrew Wakefield, was flawed and later discredited, although widely publicized in the United Kingdom. National rates of MMR immunization in Britain fell from 92 percent to 73 percent following publication, resulting in measles outbreaks and the first measles death in the U.K. in more than a decade.
The Children's Hospital study set out to provide the first population estimates of MMR vaccination rates in the U.S. following publication of the Wakefield study and its subsequent media coverage. According to the data, nearly 1 in 50 U.S. children missed the opportunity for MMR immunization in the two years following the Wakefield publication. In private physician practices non-immunization rose as high as 1 in 40 children.
Significant mainstream media coverage of the MMR-autism controversy did not begin in the U.S. until almost two years after the Lancet paper. By that time, the number of children not receiving their MMR vaccinations was returning to the pre-Wakefield study level. Children were identified as intentionally missing MMR vaccinations if they were up to date for other childhood immunizations including hepatitis B, polio, diphtheria, tetanus, pertussis and Haemophilus influenzae, but not MMR. The current study looked at immunization rates through 2004.
The decision to immunize children is influenced by three things: the parents' willingness, the health care provider's attitude and input toward guiding the decision, and the vaccine's availability. Since there was no supply shortage during the study period, the decline can only be attributed to either the parents' or the health care provider's reluctance to vaccinate. Some medical providers, made aware of the Wakefield study, may initially have become hesitant to administer the MMR vaccine, said the authors.
"The lesson for the public health community may be that the willingness to immunize a child is a story played out in the examination room during private conversation between the doctor and family," said Smith. "Updating the doctor with the most credible information and with strategies for discussing vaccine safety with parents may be the most efficient way to guarantee successful immunization practices in the face of increasing amounts of often unreliable and misleading information."
Co-authors in the study are Susan S. Ellenberg, Ph.D., from the University of Pennsylvania School of Medicine, Louis M. Bell, M.D. and David Rubin, M.D., MS.C.E, at The Children's Hospital of Philadelphia.
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