Household exposure to varicella infection only offers modest protection against herpes zoster infection in adults, a large self-controlled case series study has shown. Data were derived from the Clinical Practice Research Datalink (CPRD) which covers 9% of the UK population registered at more than 700 general practices. A total of 9,604 adults  with a diagnosis of herpes zoster, documented in primary care or hospital records, between 1997 and 2018, and who had lived with a child with a diagnosis of varicella were identified for the study.