Effectiveness of Monovalent Rotavirus Vaccine Among Young Children in Pakistan: a Test-Negative Case-Control Evaluation

BackgroundPakistan ranks among top 4 countries with greatest number of rotavirus deaths among young children. To reduce the burden of severe rotavirus disease, Pakistan began rolling out the monovalent oral rotavirus vaccine, Rotarix (RV1), in late 2017 and reached all areas by April 2018, using a 2-dose schedule at ages 6 and 10 weeks. MethodsDuring April 2018 through March 2023, we performed active surveillance for acute rotavirus gastroenteritis resulting in intravenous hydration at 9 hospital in 3 provinces among children eligible to have received rotavirus vaccine. Cases were children whose stool sample tested positive for rotavirus by enzyme immunoassay and controls were those testing negative. Unconditional logistic regression was used to estimate the effectiveness of 2 doses of RV1 vs 0 doses in reducing likelihood of hospital care for rotavirus disease. ResultsOver 2900 children were enrolled and had an analyzable vaccination record obtained. Based on 517 rotavirus cases and 1310 controls, the effectiveness of 2 RV1 doses among children aged 22 weeks-11 months was 33% (95% CI 12, 49); the effectiveness was 45% (95% CI 21, 62) among those better nourished by weight-for-age z-score (WAZ>-2). Among children aged 1 year, the effectiveness was 24% (95% CI -20, 52). A wide array of genotypes were detected and nearly 40% of cases had >1 G and/or P genotype identified. Vaccine effectiveness point estimates were lowest for those with genotype P[4] detected vs those with P[8] or P[6] detected. Conclusion2 RV1 doses appear to provide fair protection in this very high burden setting. Additional vaccination strategies should continue to be pursued for children in this and similar locations.