Adding to the overwhelming evidence that vaccines and autism are unrelated, a new study published in the child health-themed issue of the journal JAMA concludes that the measles-mumps-rubella (MMR) vaccine is not associated with increased risk of autism spectrum disorder (ASD) even among children at high risk for the disorder, notably children with siblings with autism.
Note the researchers of the present study including Dr. Anjali Jain of the The Lewin Group of Falls Church, Virginia:
“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.”
Add the researchers:
“Lower vaccination levels threaten public health by reducing both individual and herd immunity and have been associated with several recent outbreaks of measles, with most cases occurring among unvaccinated individuals.”
For the present study, the researchers used a US administrative claims database linked to a large commercial health plan to assess MMR vaccine status and ASD occurrence among 95,727 children with older siblings. Of the total number of children in the study, 1,929 had an older sibling diagnosed with ASD.
During the time period of the study, 994 (1.04%) children were diagnosed with ASD. Of the total ASD diagnoses, 134 (6.9%) occurred among children with an older sibling with the disorder and 860 (0.9%) among children without an older sibling with ASD.
Among children without an older sibling with ASD, 78,564 (84%) had received at least one dose of the MMR vaccine at age 2 and 86,063 (92%) at age 5. Among children with an older sibling with ASD, MMR vaccination rates were lower with 1,409 (73%) vaccinated at age 2 and 1,660 (86%) at age 5.
Using the Cox proportional hazards model to assess ASD risk among vaccinated children , the researchers determined that the MMR vaccine, in neither one nor two doses, increased the risk of ASD.
State the researchers:
“We also found no evidence that receipt of either one or two 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.”
Concluding, “These findings indicate no harmful association between MMR vaccine receipt and ASD even among children already at higher risk for ASD.”
Comments Dr. Brian H. King of the University of Washington and Seattle Children’s Hospital in an accompanying editorial:
“Although the evidence is already abundant that no relationship exists in the general population between MMR vaccine receipt and ASD risk, immunization rates remain low in certain populations and countries because of this inappropriate belief.
“Jain and colleagues evaluated two questions in their large insurance claims database. Does the incidence of ASD differ in younger siblings of affected children who are immunized with MMR versus those who are not? And, for the population as a whole, does the incidence of ASD vary as a function of MMR immunization status? The answer to both questions is no.
“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.”
Another study from 2014 also found strong evidence that MMR vaccine is not associated with autism.
References
Autism occurrence by MMR vaccine status among US children with older siblings with and without autism: http://jama.jamanetwork.com/article.aspx?doi=10.1001/jama.2015.3077
MMR vaccine and autism: study finds ‘no harmful association’: http://www.medicalnewstoday.com/articles/292686.php
Promising forecast for autism spectrum disorders: http://jama.jamanetwork.com/article.aspx?doi=10.1001/jama.2015.2628
Image Credits
Young Child Receiving Vaccine: https://www.flickr.com/photos/dfid/5815109843/
