No
association found between MMR vaccine and autism, even among children at higher
risk
JAMA - Journal of the American Medical Association, Science Daily
In a study that included approximately 95,000 children with
older siblings, receipt of the measles-mumps-rubella (MMR) vaccine was not
associated with an increased risk of autism spectrum disorders (ASD),
regardless of whether older siblings had ASD, findings that indicate no harmful
association between receipt of MMR vaccine and ASD even among children already
at higher risk for ASD, according to a study in the April 21 issue of JAMA,
a theme issue on child health.
Although a substantial body of research over the last 15 years
has found no link between the MMR vaccine and ASD, parents and others continue
to associate the vaccine with ASD. Surveys of parents who have children with
ASD suggest that many believe the MMR vaccine was a contributing cause.
This belief,
combined with knowing that younger siblings of children with ASD are already at
higher genetic risk for ASD compared with the general population, might prompt
these parents to avoid vaccinating their younger children, according to
background information in the article.
Participants included children continuously enrolled in the health
plan from birth to at least 5 years of age during 2001-2012 who also had an
older sibling continuously enrolled for at least 6 months between 1997 and
2012.
Of the 95,727 children included in the study, 1,929 (2.01
percent) had an older sibling with ASD.
Overall, 994 (1.04 percent) children in
the cohort had ASD diagnosed during follow-up. Among those who had an older
sibling with ASD, 134 (6.9 percent) were diagnosed with ASD, compared with 860
(0.9 percent) diagnosed with ASD among those with siblings without ASD.
The MMR
vaccination rate (l dose or more) for the children with unaffected siblings
(siblings without ASD) was 84 percent (n = 78,564) at 2 years and 92 percent (n
= 86,063) at age 5 years. In contrast, the MMR vaccination rates for children
with older siblings with ASD were lower (73 percent at age 2 years and 86
percent at age 5 years).
Analysis of the data indicated that MMR vaccine
receipt was not associated with an increased risk of ASD at any age.
"Consistent with studies in other populations, we observed
no association between MMR vaccination and increased ASD risk among privately
insured children. We also found no evidence that receipt of either 1 or 2 doses
of MMR vaccination was associated with an increased risk of ASD among children
who had older siblings with ASD.
"As the prevalence of diagnosed ASD increases,
so does the number of children who have siblings diagnosed with ASD, a group of
children who are particularly important as they were undervaccinated in our
observations as well as in previous reports," the authors write.
Editorial: Promising Forecast for Autism Spectrum Disorders
In an accompanying editorial, Bryan H. King, M.D., M.B.A., of
the University of Washington and Seattle Children's Hospital, Seattle, comments
on the findings of this study.
"Some parents of children with ASD may have chosen to delay
immunization in subsequent children until they were certain any risk had
passed. Such behavior, which arguably could enrich the immunization rate in the
nonautism subgroup relative to the group that may have been showing early
atypical development, might create the impression that MMR vaccine is actually
reducing risk for ASD.
"Indeed, Jain et al report relative risks of less than
1.0. Even so, short of arguing that MMR vaccine actually reduces the risk of
ASD in those who were immunized by age 2 years, the only conclusion that can be
drawn from the study is that there is no signal to suggest a relationship
between MMR and the development of autism in children with or without a sibling
who has autism."
"Taken together, some dozen studies have now shown that the
age of onset of ASD does not differ between vaccinated and unvaccinated
children, the severity or course of ASD does not differ between vaccinated and
unvaccinated children, and now the risk of ASD recurrence in families does not
differ between vaccinated and unvaccinated children."
Story Source:
The above story is based on materials provided by JAMA - Journal of the American
Medical Association. Note: Materials may be edited for
content and length.
Journal References:
Anjali Jain, Jaclyn Marshall, Ami Buikema, Tim Bancroft,
Jonathan P. Kelly, Craig J. Newschaffer. Autism Occurrence by MMR Vaccine
Status Among US Children With Older Siblings With and Without Autism. JAMA,
2015 DOI:10.1001/jama.2015.3077
Bryan H. King. Promising Forecast for Autism Spectrum
Disorders. JAMA, 2015 DOI: 10.1001/jama.2015.2628
Cite This Page:
JAMA - Journal of the American Medical Association. "No
association found between MMR vaccine and autism, even among children at higher
risk." Science Daily,
21 April 2015. <www.sciencedaily.com/releases/2015/04/150421111240.htm>.