Thimerosal debate

The latest salvo has been fired in the battle over whether the vaccine preservative thimerosal poses a danger to children, in particular whether it has caused the autism epidemic in the U.S. In the past 20 years, autism has increased from 1 in 10,000 to 1 in every 166 children in America.

Dr. Paul Offit, chief of the section of infectious diseases at the Children's Hospital of Philadelphia, defended the ethylmercury-containing preservative in a national conference call with reporters last week. The press briefing came a week after a study in The Journal of American Physicians found a 22 percent drop in the occurrence of autism after California ordered thimerosal eliminated from childhood vaccinations.

Offit attacked the study's data and worried that fears about thimerosal would prevent some parents from having their children vaccinated against influenza. Thimerosal no longer is used in childhood vaccines with the exception of some influenza vaccines. Influenza vaccines containing no thimerosal are also available.

Thimerosal was used initially because it prevented contamination in multi-dose vials of vaccines. Contamination isn't a concern in single-dose vials.

The Centers for Disease Control continues to maintain that no scientific evidence exists to link thimerosal with autism, but the government has reduced its use to soothe the concerns of parents.

We wonder why experts are still trotted out to defend thimerosal now that the preservative no longer is used in childhood vaccines. Maybe it's because Dr. Offit shares a patent on a rotavirus vaccine containing thimerosal and has a research grant from Merck & Co., the giant pharmaceutical company.

Questioned about this conflict of interest by Robert F. Kennedy Jr., a senior attorney for the Natural Resources Defense Council, Dr. Offit, who advises the CDC on vaccines, responded: "Science is best left to scientists."

Researchers outside of government, however, charge that the CDC was asleep at the switch during the 1990s when the schedule of childhood immunizations was dramatically increased from the three previous vaccines -- polio, diphtheria-tetanus-pertussis and measles-mumps-rubella -- to a total of 22 immunizations. They argue the cumulative effect has been devastating to some infants' neurological systems.