Tuesday, October 2, 2001; Page A07

Vaccine Preservative Still in Doubt

Scientists are still unable to determine if there is a link between a mercury-containing preservative used in some vaccines and disorders in children, the National Academy of Sciences said yesterday.

The ingredient, thimerosal, has been removed from most vaccines and the academy said that, despite the lack of proof that it is a hazard, prudence dictates that steps be taken to further reduce its use.

Safe Minds, an advocacy group working to reduce children's exposure to mercury, welcomed the report but contended it didn't go far enough. Safe Minds president Sallie Bernard said the group is pleased the report acknowledges the possibility of the preservative being linked to health problems. But she said the group is renewing its call for removal of all childhood vaccines containing thimerosal.

The connection between exposure to high levels of mercury and problems with the nervous system has long been known. While thimerosal contains a different form of mercury than the one that has been implicated in nervous disorders, critics have complained that it also may pose a hazard. Thimerosal was used for many years to prevent bacterial contamination of vaccines. Currently, however, few vaccines given to children in the United States contain the product.

It was never used in vaccines against measles, mumps, rubella, chicken pox and polio. However, until recently, some other vaccines on the recommended childhood immunization list used it.

They are now manufactured without thimerosal, but a small number of doses for hepatitis B; diphtheria, tetanus and pertussis; and influenza type B with thimerosal may still be on clinic shelves, according to the report by the academy's Institute of Medicine.

Molecule Starves Cancerous Tumors

Scientists have developed a molecule that appears to make cancer its own worst enemy.

In laboratory tests on mice, the molecule -- called "icon" -- killed tumors by destroying the blood vessels that feed them. It also caused the cancers to produce copies of icon, which spread through the body and attacked other cancers.

The process eliminated human melanoma and prostate cancers in the tested mice. The first trials in people are planned for next year.

Drugs that inhibit the growth of the blood vessels that feed cancer have received wide attention in recent years, though early results reported last spring showed less promise than had been hoped for.

The new therapy, developed by researchers Alan Garen and Zhiwei Hu at Yale University, takes a different approach, attacking the cells lining the blood vessels in tumors rather than trying to prevent the growth of new blood vessels.

Their findings are reported in today's issue of Proceedings of the National Academy of Sciences.

Albert Deisseroth of the Sidney Kimmel Cancer Center in San Diego is arranging clinical trials, which he hopes to launch next spring once approval is obtained from the Food and Drug Administration.

-- Compiled from reports by the Associated Press

© 2001 The Washington Post Company