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

Abstract

Background: 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).

Methods: 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.

Findings: 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%).

Interpretation: 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.