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As a pivotal paper linking childhood vaccinations to autism is discredited, a new study finds no evidence that the measles vaccine—given alone or as part of a combined measles, mumps, and rubella (MMR) vaccine—increases the risk of autism in children. The study appears in the Pediatric Infectious Disease Journal.
The early online publication appears in the wake of the recent announcement that the editors of The Lancet had retracted a controversial 1998 article suggesting that vaccines contributed to autism risk. That paper—which alarmed parents worldwide and led to sharp drops in measles and MMR vaccination rates in some places—has since been debunked amidst allegations of ethical and scientific misconduct.
In the new study, a team led by Dorota Mrożek-Budzyn, PhD, of Jagiellonian University Collegium Medicum, in Krakow, Poland, compared 96 Polish children with autism to a carefully matched set of 192 children without autism. Statistical techniques were used to look for any relationship between measles vaccination and the development of autism.
The results showed no evidence that children receiving measles vaccine—alone or as part of the MMR vaccine—were more likely to develop autism. This was so after adjustment for known risk factors for autism, including the mother's age and education, length of gestation, medications during pregnancy, and the child's condition after birth.
Vaccinated children were actually less likely to develop autism—especially those receiving the MMR vaccine. The researchers suspect this may reflect some other unmeasured factor affecting the children's health status. "For example," they write, "healthcare workers or parents may have noticed signs of developmental delay or disease before the actual autism diagnosis and for this reason have avoided vaccination."
The new Polish study will appear in print in the May issue of the Pediatric Infectious Disease Journal but was posted online early after the Lancet retraction was announced. The retracted study, led by Dr. Andrew Wakefield, purported to show evidence of "developmental regression" in children shortly after they received the MMR vaccine. Subsequent studies have provided little or no support for the hypothesis that MMR vaccine increases autism risk. The retraction follows allegations of ethical and scientific misconduct by Wakefield.
In Poland, the MMR vaccine has replaced the measles-only vaccine gradually over the past decade, providing a unique opportunity to compare their effects. Vaccination rates in Poland have remained high, in contrast to other countries—including the United States and Britain—where a decline in the number of children vaccinated has been followed by measles outbreaks. Based on the new results, "both vaccines are characterized by a similar level of safety with respect to the risk of autism in children," Mrożek-Budzyn and colleagues conclude.