Published in the British Medical Journal, a self-controlled case series has assessed data from the UK Clinical Practice Research Datalink (CPRD) on the protective effect of exposure to a child with varicella, on the relative incidence of herpes zoster in adults.
Primary care or hospital records between 1997 and 2018, revealed 9,604 adults, 6,584 (68.6%) women, with a diagnosis of herpes zoster, who had a child in the household with a varicella record.
The median age at zoster diagnosis was 41.1 years, and first known exposure to varicella was 38.3 years. The median age of children at varicella episode was 3.8 years. The median observation period was 14.7 years.
After adjusting for age, calendar time, and season, strong evidence suggested that in the two years after household exposure to a child with varicella, adults were 33 per cent less likely to develop zoster compared with baseline (unexposed) time.
In the 10-20 years after exposure, this protective effect waned slightly but adults were still 27 per cent less likely to develop zoster compared with baseline. A stronger boosting effect was seen among men than among women after exposure to varicella.