Immunization

Public fears about the possibility of adverse central nervous system effects of immunizations have followed several routine childhood vaccines. In the 1970s there were concerns over neurologic side effects (primarily, encephalopathy) of pertussis vaccination. In the mid-1990s there were concerns over central nervous system demyelinating disease (e.g., Guillain-Barré syndrome, multiple sclerosis) and the hepatitis B vaccine. While concerns over pertussis and hepatitis B vaccines have largely diminished in the United States, fear increased in the late 1990s over a possible association between autism and the MMR vaccine.

Controversy over the MMR vaccine followed publication of an article in the journal Lancet in early 1998 written by Andrew Wakefield. Based on observations and investigations made in twelve children, the authors suggested a link among the MMR vaccine, chronic intestinal inflammation, and autism.

Two subsequent epidemiologic studies, by B. Taylor and L. Dales, failed to identify an association between the MMR vaccine and autism. The Taylor study, from the United Kingdom, demonstrated increasing rates of autism, but a comparison of rates before and after the MMR vaccine was introduced in the United Kingdom in 1988 failed to uncover a link between the two. The Dales study, from California, demonstrated an almost fourfold relative increase (373%) in autism between 1980 and 1994. Immunization rates, however, increased by only 14 percent during the same period.

Until the cause or causes of autism are better defined, controversy will continue in this area. Currently, there is little, if any, scientific evidence linking the MMR vaccine and autism. Meanwhile, the global eradication of measles is still a possibility through widespread use of measles-containing vaccines. Eradication of measles would eliminate the estimated 880,000 deaths that occur worldwide as a result of measles infection.