A randomized controlled trial of the effectiveness of a community-based rabies vaccination strategy

Abstract

Background: Approximately 60,000 people die from dog-mediated rabies annually. Low and heterogeneous coverage reduces the effectiveness of dog vaccination campaigns that can eliminate rabies. Campaigns typically involve teams travelling annually to villages to deliver cold chain stored vaccines from centralized headquarters. Thermotolerant vaccines enable novel decentralized delivery of locally-stored vaccines by communities throughout the year. We compared the effectiveness of annual team-based versus continuous community-based dog vaccination strategies.

Methods: We conducted a cluster randomized controlled trial across Mara region, Tanzania. Trial clusters were administrative wards (112, on average four villages each). For the team-based arm vaccinators hosted annual static-point clinics, whilst for the community-based arm, a ward-based animal health officer with a village community leader managed vaccinations using vaccines stored within the ward. We measured vaccination coverage, the primary outcome, twice annually per cluster (month 1 and 11) through household surveys over three years (November 2020 to October 2023) and examined spatial and temporal coverage variations as secondary outcomes.

Findings: Community-based delivery achieved significantly higher coverage (49-62%) than team-based delivery (22-46%), and consistently exceeded the critical threshold for herd immunity (40%), Odds ratio (OR): 1.48-3.49. The lower less uniform coverage achieved through team-based delivery had a higher monthly probability of falling below the critical threshold (0.6, 95% CI: 0.38-0.81) vs 0.18 (95% CI: 0.04-0.40). Greater declines in coverage over the year were recorded in the team-based arm compared to the community-based.

Conclusion: Community-based mass dog vaccination achieves higher more consistent coverage than team-based delivery across settings typical of many sub-Saharan African countries. This approach could play an important role in national rabies elimination programmes aiming to end human rabies deaths by 2030 as part of the global 'zero by 30' strategy.

Figure 1.

Study area in Tanzania. Districts and wards are shown with thick and thin black lines, respectively. The RCT took place in target districts colored red. Grey area indicates wards where on-going MDV had recently targeted

Figure 2.

Number of rabies vaccinations performed (lower series; total = 186,931) and number of dogs surveyed (upper series; total = 25,677) per day by trial arm.

Figure 3.

Estimated coverage ± 95% confidence limits at each survey time point, by trial arm.

Figure 4.

Estimated intervention effect (community:team) odds ratios ± 95% confidence limits at each survey time point.

Figure 5.

Estimated probability distribution of coverage by trial month for each arm. The coverage target of 40% is shown by a dashed line. White circles indicate medians and quartiles and range are shown by box-and-whisker plots.