When chickenpox strikes children undergoing steroid therapy, a disease typically viewed as an elementary schooler's rite of passage can become a potential killer. That's the finding of a recent study published in October's edition of Pediatrics. Steroids are a common therapy in treating childhood leukemia, and are also used in treating severe asthma. But the drugs suppress the immune system and allow for a more severe infection by the varicella virus—the human herpes 3 virus that causes chickenpox and, in adults, shingles. Named for the chickpea-like red bumps on the skin, chickenpox affects about four million people every year, and kills about 100.

The nine-year study by a team from Brenner Children's Hospital in Winston-Salem, N.C., tracked 697 patients with acute leukemia. Of the 110 (about 16%) who contracted chickenpox, 54 had severe cases of infection. Severity was determined on a scale from 1 to 5, where grade 1 and 2 were classified as non-severe (either asymptomatic or mild to moderate symptoms); grades 3, 4 and 5 were considered severe and ranged from hospitalization to life-threatening. Two children died during the course of the study. Of children who contracted chickenoix within a three-week period following steroid treatment, 70% developed severe chickenpox; in those who developed chickenpox after that period, 44% had severe cases. The current study deals only with children with leukemia, but researchers say the findings may be relevant in other cases where steroid therapy is used.

Chickenpox is a one-time inconvenience to which many parents try to expose their children (even going so far as to throw chickenpox parties) in order to avoid a future infection in adulthood, where chickenpox becomes a much more serious condition. A chickenpox vaccine that is 85% effective has been available since 1995 for healthy kids, but those with compromised immune systems might have a severe reaction to it-since the vaccine itself is a live virus.

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01/21/02   Vaccines Stage a Comeback