Monovalent Rotavirus Vaccine Effectiveness and Impact on Rotavirus Hospitalizations in Zanzibar, Tanzania: Data From the First 3 Years After Introduction.

Background: Low-income settings challenge the level of protection provided by live attenuated oral rotavirus vaccines. Rotarix (RV1) was introduced in the United Republic of Tanzania in early 2013, with 2 doses given at the World Health Organization-recommended schedule of ages 6 and 10 weeks, along with oral poliovirus vaccine.
Methods: We performed active surveillance for rotavirus hospitalizations at the largest hospital in Zanzibar, Tanzania, from 2010 through 2015. Using a case-test-negative control design, we estimated the vaccine effectiveness (VE) of 2 RV1 doses in preventing rotavirus hospitalizations.
Results: Based on 204 rotavirus case patients and 601 test-negative controls aged 5-23 months, the VE of 2 RV1 doses against hospitalization for rotavirus diarrhea was 57% (95% confidence interval, 14%-78%). VE tended to increase against hospitalizations with higher severity, reaching 69% (95% confidence interval, 15%-88%) against the severity score for the top quarter of case patients. Compared with the prevaccine period, there were estimated reductions of 40%, 46%, and 69% in the number of rotavirus hospitalizations among infants in 2013, 2014, and 2015, respectively, and reductions of 36%, 26%, and 64%, respectively, among children aged <5 years. Conclusions: With data encompassing 3 years before and 3 years after vaccine introduction, our results indicate that successful delivery of RV1 on the current World Health Organization schedule can provide substantial health benefits in a resource-limited setting. Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US