The controversial theory that childhood vaccines cause autism was discredited by one report after another this year. The biggest blow came with the public retraction of a 1998 paper in the British medical journal The Lancet that had suggested a link between the measles-mumps-rubella vaccine and autism in a study of 12 children. Despite questions at the time concerning its scientific credibility, the report garnered a blizzard of press coverage and led some parents to put off vaccinating their young children.
In February Richard Horton, editor of The Lancet, said that the work was “flawed” and should never have been published. More reports followed. In May an expert panel at the Washington-based Institute of Medicine announced that neither the measles-mumps-rubella vaccine nor the mercury-based vaccine preservative thimerosal is associated with autism. The panel based its finding on expert testimony, published papers, and ongoing and completed research—including epidemiological studies in the United States, the United Kingdom, and Sweden. Then in September a long-term study of more than 5,000 children in the United Kingdom—published in The Lancet—also found no association between measles-mumps-rubella shots and autism.
The new evidence has yet to quell the fears of some parents. In particular, uncertainty over the effects of exposure to mercury have made thimerosal a continued focus of controversy.
Arguing that the slightest risk warrants completely eliminating the preservative, the Food and Drug Administration recommended removing it from childhood vaccines. Today, except for the flu vaccine manufactured by Aventis, most vaccines contain only trace amounts of thimerosal or none.
Experts say it’s crucial to win back parents who mistrust the government and refuse to have their kids vaccinated. “But there is no way we can assure them that every vaccine is safe for every child,” says Christopher Wilson, chair of immunology at the University of Washington in Seattle. “That’s not the case and never will be.”