The epidemiology of chickenpox in UK 5-year olds: An analysis to inform vaccine policy

Varicella vaccine is not routinely administered to children in many countries including the UK. Longitudinal data are lacking to inform optimal schedules. We report the prevalence of VZV infection at 5 years of age, cumulative incidence between 3 and 5 years and socio-demographic associations with risk of infection using longitudinal data on 12,509 children from the UK Millennium Cohort Study. VZV prevalence by 5 years was 76.9% [95% CI: 75.9%, 78.0%]. The cumulative incidence between 3 and 5 years was 32.2% [95% CI: 31.1%, 33.3%]. Risk of infection by 5 years was associated with higher maternal socio-economic status, larger household size and formal day-care attendance at 9 months and 3 years. If universal varicella immunisation were introduced in the UK, where 40% children have attended some formal day-care by 3 years, a schedule commencing early in the second year of life would be indicated.