Rotavirus vaccination effectiveness: a case-case study in the EDICS project, Castellón (Spain).

In Spain, in 2006, two oral live-attenuated vaccines against rotavirus disease were licensed for infants up to 6 months. Recent data suggest that vaccine efficacy may vary by region. This makes the real-life postmarketing monitoring of rotavirus vaccination effectiveness an important aspect of rotavirus epidemiologic surveillance. We carried out a case-case study to assess the rotavirus vaccination effectiveness in children from 2 to 35 months of age during the year 2009 in Castellón. As a second- and counterfactual objective to evaluate the possible selection bias and the specificity of the association, we evaluated the "effectiveness" of pneumococcal vaccination against rotavirus diarrhea. Cases were 71 children with confirmed rotavirus gastroenteritis, and controls were 261 children with positive results to any other organism that was not rotavirus. The immunization status of each child, the number of doses and dates of vaccination were assessed by consulting the Regional Immunization Registry. The lowest proportion of vaccinated cases was observed among rotavirus diarrhea (2.8%). The proportion of vaccinated children among the control group was 21.8%. The effectiveness of vaccination with at least one dose of vaccine against rotavirus was 87.7% (45.5-99.7%). If we restrict the analysis to non-hospitalized children, this figure was slightly lower, 83.5% (25.4-96.3%). As expected, pneumococcal vaccination was not protective against rotavirus infection showing the specificity of the association found. The immunization information systems in combination with population-based studies of the incidence of infectious gastroenteritis, such as EDICS offer appropriate conditions for postmarketing monitoring of vaccine effectiveness. Published by Elsevier Ltd.