Effectiveness of community-based delivery of mass dog vaccination to prevent rabies: A cluster randomized controlled trial.

Abstract

Approximately 60,000 people die from rabies annually, mostly in Africa and Asia. Mass dog vaccination is critical for elimination. Herd immunity has been calculated to be attained when >40% (critical threshold) of dogs are vaccinated. A common delivery method implemented in Tanzania and other countries typically involves non-local teams travelling to villages implementing dog vaccination annually through static-point clinics using cold chain stored vaccines (Team-based delivery). Determination that a canine rabies vaccine is thermotolerant enables novel Community-based dog vaccination strategies whereby community vaccinators use vaccines stored locally throughout the year (Community-based delivery). Two dog vaccination strategies were compared using a three-year cluster randomized controlled trial in Tanzania (Clinical Trials Registration Number ISRCTN14813279). The strategies were designed to represent implementation using resources typical of government-led initiatives. Wards (n = 112) were randomly assigned to either Team-based delivery or Community-based delivery. Coverage was estimated using household surveys implemented biannually. Mean coverage achieved by Community-based delivery (55%; 95% Confidence Interval (CI): 45-65%) was higher than Team-based delivery (37%; 95% CI: 28-46%). Moreover, because coverage was lower and declined over each year only in Team-based delivery, the probability of coverage being below the critical threshold was higher for Team-based delivery (60%) compared to Community-based delivery (18%). To ensure coverage does not dip below the critical threshold by the year end, coverage at the start of the year in Team-based delivery needed to be higher (61%) than in Community-based (42%). Community-based delivery achieved higher and more consistent vaccination coverage across a range of settings typical of many sub-Saharan African countries. Generalisation to different sociocultural/ agroecological settings requires further evidence. Although direct evidence on impact on rabies elimination was not measured, this approach could play a role in national elimination strategies, developed for the global 'Zero by 30' strategy to end dog-mediated rabies deaths by 2030, and in response to investment by Gavi, the vaccine alliance.