Two shots better for preventing chicken pox

A chicken pox outbreak at a day care center two years ago found vaccinations surprisingly ineffective and may suggest that children should get two shots instead of one, researchers say.

Dr. Karin Galil, lead author of the study in today's New England Journal of Medicine, and other experts said it is much too early to propose such a change.

"When there are 20 or 30 estimates, we'll have a better measure of how well it's truly working," said Galil, who was an epidemiologist for the Centers for Disease Control and Prevention when she studied the outbreak and now works for a company developing a new antibiotic.

Seven earlier studies found the vaccine protected at least 71 percent of the children who got shots from developing the disease and kept the disease minor in nearly all those infected by the virus.

But the latest study tracked by far the worst performance of a vaccine that has cut the number of U.S. chicken pox cases by 80 percent since it was introduced in 1995.

The outbreak was at a day care center near Concord, N.H. A boy who had been vaccinated three years earlier came down with the virus on Dec. 1, 2000. By Jan. 11, 2001, it had spread to 24 other children -- including 17 who also had been vaccinated.

About two-thirds of the children had been vaccinated; six of seven unvaccinated children in the boy's class got sick.