No scientific link between childhood vaccines and autism

A new article recently published in the Journal for Specialists in Pediatric Nursing explored vaccination history, vaccine safety monitoring systems in the U.S., and the two most publicized theoretical vaccine-related exposures associated with autism -- the vaccine preservative thimerosal and the measles, mumps, and rubella (MMR) vaccine. A review of published research shows that there is not convincing scientific evidence supporting a relationship between vaccines and autism. The article is part of a special issue, which includes five articles focusing on the topic of autism.

By definition, the onset of autism occurs prior to age three. No clear cause of autism has been identified, although various possible associations have been examined. There has been growing interest in environmental exposures, including vaccinations. Childhood vaccinations are administered as early as possible to assure that infants are protected against diseases that occur in early childhood. This time period often coincides with the time period that autism may be suspected or diagnosed.

A British paper published about 10 years ago seemingly made the claim that receipt of the MMR vaccine was associated with autism.
This initial report of a possible relationship between the MMR vaccine and the onset of autism received significant attention, and in England, MMR immunization rates dropped and the number of measles cases rose dramatically over the next decade.

In response to this concern in the U.S., the CDC and NIH examined vaccine safety issues and after performing an in-depth review of the relevant literature, rejected a causal relationship between the MMR vaccine and autism. Eventually most of the authors of the original British paper also asked to retract the interpretation of their findings.

Concerns have also been raised about thimerosal, a preservative in multidose vaccines that was removed from routine vaccines in 2001 in the US and in 1992 in Denmark and Sweden. Despite the removal in Denmark and Sweden, autism rates have continued to increase there. Other studies have failed to find a link as well. Finally, in February 2009, the U.S. Court of Federal claims found that the MMR vaccine and thimerosal containing vaccines were not causal factors in the development of autism.

"Nurses are often in the unique position of providing advice regarding vaccines in their formal practice areas as well as in their daily lives," the authors note. "It is thus imperative that they have knowledge of the research and its results when discussing vaccines with parents, peers, and medical health professionals."

October 8, 2009