HEALTH & SCIENCE

Chicken pox vaccine's staying power questioned

A disease outbreak in a New Hampshire day-care center may indicate the need for periodic boosters.

By Victoria Stagg Elliott, AMNews staff. Jan. 20, 2003.

The 4-year-old boy was healthy and had received all of his shots, including the one for varicella three years before. But one morning at a day-care center in a small town near Concord, N.H., his body erupted in a rash and he was sent home.

The boy had chicken pox and had infected more than a dozen of his classmates with the illness, even though most had also received the vaccine. Within two months, another dozen would also be diagnosed with what was, until the 1995 licensure of the varicella vaccine, one of the leading causes of morbidity among children.

This was not supposed to happen, according to a case study published in the New England Journal of Medicine last month.

"They were so healthy as a group," said Karin Galil, MD, MPH, the lead researcher who investigated the outbreak while a medical epidemiologist at the Centers for Disease Control and Prevention. "And a lot of the risk factors associated with vaccine failure, such as asthma, just weren't present."

Dr. Galil and her fellow CDC investigators found the vaccine still prevented the most severe forms of chicken pox, but that children who had received it more than three years earlier were most at risk for developing mild or moderate forms of the disease.

An editorial accompanying the article suggests considering whether a booster shot may be needed a few years after the initial dose.

"This outbreak constitutes a warning signal," wrote Anne A. Gershon, MD, director of the infectious disease division at Columbia University College of Physicians and Surgeons in New York. " The time for exploring the possibility of routinely administering two doses of varicella vaccine to children seems to have arrived."

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