Effectiveness of the monovalent rotavirus vaccine in Colombia: a case-control study

Objective: To assess the effectiveness of the monovalent rotavirus vaccine (RV1) to prevent rotavirus diarrhea admissions to emergency departments (ED) in Colombia.

Methods: A multicenter case-control study was carried out in six Colombian cities from 2011 to January, 2013. Cases were laboratory confirmed rotavirus diarrhea patients admitted to ED of selected health centers. Controls were patients with non-rotavirus diarrhea. Vaccination status was card-confirmed. Vaccine effectiveness and 95% confidence intervals (CI) were calculated from the conditional logistic regression models using the formula 1-adjusted odds ratio×100.

Results: 1051 fecal samples were collected from 193 cases and 858 controls. Vaccination history was confirmed on 173 cases (90%) and 801 controls (93%). Among the rotavirus-positive samples with vaccination history, 57% were G2P[4], 9.8% G9P[8], 6% G9P[6]. Median age of cases (17 months) was greater than controls (15 months) (P<0.001), and mothers of cases had lower level of education (P=0.025). The adjusted effectiveness was 79.19% (95% CI, 23.7 to 94.32) among children 6-11 months of age and -39.75% (95% CI, -270.67 to 47.24) among those >12 months of age. Against overnight rotavirus hospitalizations, RV1 provided protection of 84.42% (95% CI, 22.68 to 96.86) among children 6-11 months of age, and -79.49% (95% CI, -555.8 to 51.08) among those >12 months.

Conclusions: RV1 provided significant protection against rotavirus hospitalization among children under 1 year of age in the Colombian setting. The observation of lower effectiveness in children >12 months requires further assessment.