Abstract
Objective: To assess the magnitude and duration of any hypothesised protective effect of household exposure to a child with varicella on the relative incidence of herpes zoster in adults.
Design: Self controlled case series.
Setting: UK general practices contributing to Clinical Practice Research Datalink.
Participants: 9604 adults (≥18 years) with a diagnosis of herpes zoster (in primary care or hospital records) between 1997 and 2018, who during their observation period lived with a child (<18 years) with a diagnosis of varicella.
Main outcome measures: Relative incidence of herpes zoster in the 20 years after exposure to a child with varicella in the household compared with baseline time (all other time, excluding the 60 days before exposure).
Results: 6584 of the 9604 adults with herpes zoster (68.6%) were women. Median age of exposure to a child with varicella was 38.3 years (interquartile range 32.3-48.8 years) and median observation period was 14.7 (11.1-17.7) years. 4116 adults developed zoster in the baseline period, 433 in the 60 days before exposure and 5055 in the risk period. After adjustment 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% less likely to develop zoster (incidence ratio 0.67, 95% confidence interval 0.62 to 0.73) compared with baseline time. In the 10-20 years after exposure, adults were 27% less likely to develop herpes zoster (0.73, 0.62 to 0.87) compared with baseline time. A stronger boosting effect was observed among men than among women after exposure to varicella.
Conclusions: The relative incidence of zoster was lower in the periods after exposure to a household contact with varicella, with modest but long lasting protective effects observed. 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 immunisation.
| Original language | English |
|---|---|
| Article number | l6987 |
| Journal | British Medical Journal |
| Volume | 368 |
| DOIs | |
| Publication status | Published - 22 Jan 2020 |
Bibliographical note
Funding Information: HF receives funding from Health Data Research UK. JB receives funding from the University College London/University College London Hospitals National Institute for Health Research Biomedical Research Centre. SML was supported by a Wellcome senior research fellowship in clinical science (205039/Z/16/Z). CWG is supported by a Wellcome intermediate clinical fellowship (201440/Z/16/Z). KB is supported by a Sir Henry Dale fellowship jointly funded by the Wellcome Trust and the Royal Society (17731/Z/15/Z). The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the funders. This work was also supported by Health Data Research UK (grant No LOND1), which is funded by the UK Medical Research Council, Engineering and Physical Sciences Research Council, Economic and Social Research Council, Department of Health and Social Care (England), Chief Scientist Office of the Scottish Government Health and Social Care Directorates, Health and Social Care Research and Development Division (Welsh government), Public Health Agency (Northern Ireland), British Heart Foundation, and Wellcome Trust. The funder had no role in the design, analysis or interpretation of this study.All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work. AF has research funding (related to meningococcal carriage) paid to the University of Bristol from GSK. RM reports grants from GSK and from Merck for a study on chickenpox epidemiology. Ethical approval: This study was approved by the independent scientific advisory committee (19_026). Data sharing: No additional data available. The lead author (HF) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.
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Publisher Copyright: © 2019 Published by the BMJ Publishing Group Limited.
Citation: Forbes H, Douglas I, Finn A, Breuer J, Bhaskaran K, Smeeth L et al. Risk of herpes zoster after exposure to varicella to explore the exogenous boosting hypothesis: self controlled case series study using UK electronic healthcare data BMJ 2020; 368 :l6987
DOI:10.1136/bmj.l6987