Vaccine Fails to Protect Preschoolers

Dec. 12, 2002 (Ivanhoe Newswire) -- A common childhood vaccine often fails to protect youngsters against disease, report researchers publishing in this week's New England Journal of Medicine. The finding could lead to a new way of administering the vaccination.

In a study of 88 children attending a day care center in New Hampshire, CDC investigators found the varicella vaccine was only 44percent effective in holding off the varicella virus, which causes a widespread rash and can lead to body-wide complications. Most of the infections were mild, indicating the vaccine still provides protection against more severe forms of the disease. But the study also showed a decreasing effectiveness of the vaccine over time.

Prior to development of the varicella vaccine, which was licensed in 1995 and is given to young children in one dose, the disease resulted in about 11,000 hospitalizations and 100 deaths each year. Rates have tapered off markedly since then. However, few studies have looked at the long-term effectiveness of the vaccine.

These researchers monitored children in a day care center, which experienced a case of varicella in a previously vaccinated child. Over the course of a year, more than half of his classmates also came down with the virus. About 66 percent of the kids in the class had previously received the vaccine. The children most likely to develop the disease were those who received the vaccination the longest ago.

Although mild cases of the disease usually clear up without problem, researchers note varicella infections can sometimes lead to a more severe disease called zoster, which is caused by a wild-type of the virus and is particularly serious in children with other medical problems, such as leukemia.

In an editorial accompanying the study, Anne A. Gershon, M.D., from Columbia University, notes the vaccine is usually given to older children and adults in two doses, and this may improve effectiveness in younger kids. Dr. Gershon writes, "The time for exploring the possibility of routinely administering two doses of varicella vaccine to children seems to have arrived."