Impact of Rotavirus Vaccine Introduction and Postintroduction Etiology of Diarrhea Requiring Hospital Admission in Haydom, Tanzania, a Rural African Setting

Background No data are available on the etiology of diarrhea requiring hospitalization after rotavirus vaccine introduction in Africa. The monovalent rotavirus vaccine was introduced in Tanzania on January 1, 2013. We performed a vaccine impact and effectiveness study as well as a qPCR-based etiology study at a rural Tanzanian hospital. Methods We obtained data on admissions among children under 5 years to Haydom Lutheran Hospital between January 1, 2010 and December 31, 2015, and estimated the impact of vaccine introduction on all-cause diarrhea admissions. We then performed a vaccine effectiveness study using the test-negative design. Finally, we tested diarrheal specimens during 2015 by qPCR for a broad range of enteropathogens and calculated pathogen-specific attributable fractions. Results Vaccine introduction was associated with a 44.9% (95% CI 17.6 - 97.4) reduction in diarrhea admissions in 2015, as well as delay of the rotavirus season. The effectiveness of two doses of vaccine was 74.8% (-8.2 - 94.1) using an enzyme immunoassay-based case definition and 85.1% (26.5 - 97.0) using a qPCR-based case definition. Among 146 children enrolled in 2015, rotavirus remained the leading etiology of diarrhea requiring hospitalization (AF 25.8%, 95% CI: 24.4 - 26.7), followed by heat-stabile enterotoxin-producing E. coli (18.4%, 12.9 - 21.9), Shigella/enteroinvasive E. coli (14.5%, 10.2 - 22.8), and Cryptosporidium (7.9%, 6.2 - 9.3). Conclusions Despite the clear impact of vaccine introduction in this setting, rotavirus remained the leading etiology of diarrhea requiring hospitalization. Further efforts to maximize vaccine coverage and improve vaccine performance in these settings are warranted.