Elsevier

The Lancet

Volume 360, Issue 9334, 31 August 2002, Pages 678-682
The Lancet

Articles
Contacts with varicella or with children and protection against herpes zoster in adults: a case-control study

https://doi.org/10.1016/S0140-6736(02)09837-9Get rights and content

Summary

Background

Whether exogenous exposure to varicella zoster-virus protects individuals with latent varicella-zoster virus infection against herpes zoster by boosting immunity is not known. To test the hypothesis that contacts with children increase exposure to varicella-zoster virus and protect latently infected adults against zoster, we did a case-control study in south London, UK.

Methods

From 22 general practices, we identified patients with recently diagnosed zoster, and control individuals with no history of zoster, matched to patients by age, sex, and practice. Participants were asked about contacts with people with varicella or zoster in the past 10 years, and social and occupational contacts with children as proxies for varicella contacts. Odds ratios were estimated with conditional logistic regression.

Findings

Data from 244 patients and 485 controls were analysed. On multivariable analysis, protection associated with contacts with a few children in the household or via childcare seemed to be largely mediated by increased access to children outside the household. Social contacts with many children outside the household and occupational contacts with ill children were associated with graded protection against zoster, with less than a fifth the risk in the most heavily exposed groups compared with the least exposed. The strength of protection diminished after controlling for known varicella contacts; the latter remained significantly protective (odds ratio 0·29 [95% CI 0·10–0·84] for those with five contacts or more).

Interpretation

Re-exposure to varicella-zoster virus via contact with children seems to protect latently infected individuals against zoster. Reduction of childhood varicella by vaccination might lead to increased incidence of adult zoster. Vaccination of the elderly (if effective) should be considered in countries with childhood varicella vaccination programmes.

Introduction

Primary infection with varicella-zoster virus causes varicella, after which the virus establishes latency in dorsal root ganglia.1, 2, 3 Reactivation of latent infection is thought to result from declining specific cell-mediated immunity, and leads to herpes zoster.4, 5, 6 Zoster occurs frequently in ageing populations and causes substantial acute and chronic morbidity, the commonest long-term complication being persistent pain (post-herpetic neuralgia).7

Hope-Simpson postulated that exogenous exposure to people with varicella or zoster might boost specific immunity and therefore decrease the risk of zoster in latently infected individuals.8 Mothers of children with varicella have cell-mediated immune boosting, and children with leukaemia seem to be protected against zoster by household exposure to varicella.9, 10 However, whether exogenous exposure protects against zoster in immunocompetent adults is unclear. In one study, paediatricians had more contacts with patients infected with varicella-zoster virus than dermatologists or psychiatrists, and were significantly less likely to have developed zoster, but the results could have been influenced by very low response rates to the survey.11

The role of immune boosting is an important issue for varicella vaccination programmes, since a reduction in childhood varicella will result in fewer exogenous exposures to varicella-zoster virus, which could lead to increased incidence of zoster among unvaccinated adults.12 Varicella vaccination has already been introduced in countries such as the USA and Japan, and is being considered by many European countries. We therefore set up a study to test the hypothesis that exogenous exposure to varicella-zoster virus protects against zoster.

Section snippets

Patients and controls

This investigation was one objective of a community-based case-control study of risk factors for zoster in immunocompetent adults in south London, UK, between September, 1997, and December, 1998. A reporting system was set up among 22 general practices to identify individuals who had recently been diagnosed with zoster by their family physician. For each patient with zoster, two controls with no history of zoster were sought by searching practice registers for individuals who were nearest in

Results

During the study period, 436 patients were identified, of whom 139 were ineligible (46 were younger than 16 years, 37 had recent immunosuppression, 18 were African, 11 were temporarily registered, four were incapable of answering questions, and 23 were identified more than 8 weeks after rash onset). Of the remaining 297 patients, 16 (5·4%) were not enrolled: 12 refused and four were away from London or repeatedly unavailable for more than 8 weeks. The eligibility of these patients was not

Discussion

The findings from this study suggest that continued exogenous exposure to varicella is protective against zoster in latently infected adults. This result is consistent with those of Gershon and colleagues,10 who found that vaccinated children with leukaemia were at significantly lower risk of zoster if they had household exposure to varicella, and that many of these children had evidence of immunological boosting. In our study, there were doseresponse effects associated with a range of

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