Case Control Study of Rotavirus Vaccine Effectiveness in Portugal during Six Years of Private Market Use

BACKGROUND:: Although recommended by the vaccine committee of the Portuguese Paediatric Society, rotavirus vaccines have not been included in the routine immunisation schedule. They have been available privately since 2006 with estimated coverage reaching approximately 30%. However unlike other European countries using the vaccine, sentinel surveillance has detected fluctuations but no clear trends in the rate of gastrointestinal disease presentations. In this study we set out to establish the real world effectiveness of rotavirus immunisation in this low vaccine coverage setting.

METHODS:: We carried out a test negative case control study on a population of children attending a regional paediatric hospital, between 2006 and 2012, with symptoms of acute gastroenteritis and producing a stool sample for routine rotavirus testing. We calculated exposure odds ratio (ratio of odds of antecedent vaccination among cases compared with controls) to derive vaccine effectiveness ((1 -adjusted odds ratio)/100) against both hospital attendance and admission.

RESULTS:: Vaccine effectiveness against attendance with rotavirus acute gastroenteritis was 83.7% (95% CI 73.9-89.8) and against hospital admission was 96.1% (95% CI 83.8-99.1). No significant difference between the two available vaccines was detected.

CONCLUSION:: Both rotavirus vaccines offer a high degree of individual protection in this population.