A population based study comparing changes in rotavirus burden on the Island of Ireland between a highly vaccinated population and an unvaccinated population.

BACKGROUND: Rotavirus infection is a leading cause of gastroenteritis in infants and children globally. Reductions in rotavirus activity have been observed following introduction of rotavirus vaccination programmes, however a reductions have also been reported in some unvaccinated countries. The Island of Ireland incorporates the two jurisdictions Northern Ireland (NI) and the Republic of Ireland (IE). Both have similarities in climate, demography, morbidity and mortality but distinct health administrations and vaccination policies. Rotarix was added to the childhood immunisation programme in NI on the 1 July 2013. IE have not introduced routine rotavirus vaccination to date. The aim of this population based ecological study was to evaluate the impact of the rotavirus vaccine on burden of rotavirus disease in NI, and to compare with IE as an unvaccinated control population. This will help determine if the changes seen were due to the rotavirus vaccine, or due to confounding factors. METHODS: A number of population based measures of disease burden were compared in both jurisdictions pre-vaccine (six years; 2007/08-2012/13) and post-vaccine (two years; 2013/14-2014/15). The data sources included national rotavirus surveillance data based on laboratory reports/notifications; hospital admission data; and notifications of gastroenteritis in under 2year olds. RESULTS: In the post-vaccination period, rotavirus incidence in NI dropped by 54% while in IE it increased by 19% compared to the pre-vaccine period. Notifications of gastroenteritis in under 2s in NI declined by 53% and hospital admissions in under 5year olds in NI declined by 40% in the post vaccine period. CONCLUSIONS: This natural experiment demonstrated a significant reduction in rotavirus disease activity post-vaccine introduction in NI with associated reductions in healthcare utilisation, with a concurrent increase in rotavirus disease activity in the non-vaccinated population in IE. These findings support rotavirus vaccination as an effective measure to reduce childhood morbidity.