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Intradermal rabies post-exposure prophylaxis can be abridged with no measurable impact on clinical outcome in Cambodia, 2003–2014

Tarantola, Arnaud, Ly, Sowath, Chan, Malen, In, Sotheary, Peng, Yiksing, Hing, Chanthy, Taing, Chun Navy, Phoen, Chandara, Ly, Sovann, Cauchemez, Simon, Buchy, Philippe, Dussart, Philippe, Bourhy, Hervé, Mary, Jean-Yves
Vaccine 2019 v.37 pp. A118
confidence interval, developing countries, disease control, dogs, necropsy, patients, people, rabies, retrospective studies, risk, transportation, vaccination, vaccines, Cambodia
Rabies causes 60,000 deaths worldwide annually. Rabies post-exposure prophylaxis is highly effective but often geographically and financially beyond reach in endemic developing countries. We conducted a retrospective study on clinical outcome at ≥6 months in 3318 Cambodians who received intradermal Vero cell vaccine post-exposure prophylaxis after a bite by a rabid or sick-looking but untested dog in 2003–2014. An external expert panel examined verbal autopsy reports to identify rabies deaths. 1739 (93.65%) persons bitten by rabid- and 1066 (72.96%) bitten by sick-looking but untested dogs were traced and 513 were lost to follow-up. Among the former, 1591 (91.49%) and 129 (7.42%) patients referred for 4+ and 3 post-exposure prophylaxis sessions, respectively. Three persons died of probable rabies so that the overall percentage of survival was 99.83% (95% exact confidence interval: 99.49–99.96%) in post-exposure prophylaxis recipients bitten by confirmed rabid dogs. No significant difference was found in survival among patients who received 3 vs. 4+ sessions (with or without rabies immunoglobin). The power of the study, however, was limited. The current four sessions/one month intradermal regimen can be reduced to a three sessions/one week at no detectable added risk to patients, with the limitation of study power at 49%. A clinical follow-up system should be adopted by rabies prevention centers, especially to monitor implementation of an abridged course. The Institut Pasteur in Cambodia regimen will improve vaccine equity by treating 33% more patients with available doses, reduce direct cost of vaccination, transportation and other indirect costs to vaccinees.