HealthDay News — The relative incidence of shingles is lower in adults after exposure to a household contact with chickenpox, but full protection is not achieved, according to a study published in The BMJ.

Harriet Forbes, from the London School of Hygiene and Tropical Medicine, and colleagues used the UK Clinical Practice Research Datalink to evaluate the protective effect of household exposure to a child with varicella on the relative incidence of herpes zoster over 20 years among 9604 adults (68.6% women) who lived with a child.

The researchers found that the median age during exposure to a child with varicella was 38.3 years and the median observation period was 14.7 years. In the 2 years after household exposure to a child with varicella, adults were 33% less likely to develop zoster (incidence ratio, 0.67) compared with baseline after adjusting for age, calendar time, and season. Development of herpes zoster was also less likely in the 10 to 20 years after exposure (incidence ratio, 0.73) vs baseline. The boosting effect after exposure to varicella was stronger among men than women.

“This study suggests that exogenous boosting provides some protection from the risk of herpes zoster, but not complete immunity, as assumed by previous cost-effectiveness estimates of varicella immunization,” the authors write.

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One author disclosed financial ties to the pharmaceutical industry.

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