Bayesian modeling of post-vaccination serological data suggests that yearly vaccination of dog aged <2 years old is efficient to stop rabies circulation in Cambodia.

Rabies control remains challenging in low and middle-income countries, mostly due to lack of financial resources, rapid turnover of dog populations and poor accessibility to dogs. Rabies is endemic in Cambodia, where no national rabies vaccination program is implemented. The objective of this study was to assess the short and long-term vaccination-induced immunity in Cambodian dogs under field conditions, and to propose optimized vaccination strategies. A cohort of 351 dogs was followed at regular time points following primary vaccination only (PV) or PV plus single booster (BV). Fluorescent antibody virus neutralization test (FAVNT) was implemented to determine the neutralizing antibody titer against rabies and an individual titer ≥0&#183;5 IU/mL indicated protection. Bayesian modeling was used to evaluate the individual duration of protection against rabies and the efficacy of two different vaccination strategies. Overall, 61% of dogs had a protective immunity one year after PV. In dogs receiving a BV, this protective immunity remained for up to one year after the BV in 95% of dogs. According to the best Bayesian model, a PV conferred a protective immunity in 82% of dogs (95% CI: 75–91%) for a mean duration of 4.7 years, and BV induced a lifelong protective immunity. Annual PV of dogs less than one year old and systematic BV solely of dogs vaccinated the year before would allow to achieve the 70% World Health Organization recommended threshold to control rabies circulation in a dog population in three to five years of implementation depending on dog population dynamics. This vaccination strategy would save up to about a third of vaccine doses, reducing cost and time efforts of mass dog vaccination campaigns. These results can contribute to optimize rabies control measures in Cambodia moving towards the global goal of ending human death from dog-mediated rabies by 2030. Author summary: Rabies is a fatal zoonotic viral disease. Dog vaccination is recognized as the most cost-effective and sustainable solution to rabies prevention. Cambodia is endemic with canine mediated rabies, that would cause to around 800 human death each year. This country also has a large owned but mostly free-roaming dog population that makes efficient massive vaccination hard to achieve. In this study, we vaccinated 351 dogs with or without booster one year later. We then used serological assessed the short and long-term vaccination-induced immunity in these dogs, and Bayesian modeling to identify a vaccination strategy adapted to the Cambodian dog population characteristics. Yearly primary vaccinations for young dogs, supplemented with a single booster injection of these dogs promises to achieve 70% dog vaccination coverage effectively and efficiently, and control rabies circulation in dog populations. Applying this new strategy running for five more years after the vaccination coverage of at least 70% is achieved, this implies per 1,000 dogs between 2000 and 5 000 saved vaccine doses depending on dog population characteristics. Our results could help controlling rabies in Cambodia and potentially be adopted by other countries facing similar challenges. [ABSTRACT FROM AUTHOR]