Rabies Post Exposure Vaccine Effectiveness: A Retrospective Case-Control Study in Amhara Region, Ethiopia

Rabies can be prevented by vaccination of dogs and provision of post exposure vaccine (PEV) for exposed subjects. There are many post exposure rabies vaccines in the market with their efficacy extending to 100%; however, there are complaints on the effectiveness of the vaccine in the field level. Therefore, the aim of this study was to assess PEV effectiveness and identify factors associated with rabies cases. A retrospective case-control study was conducted in the Amhara regional state of Ethiopia from December 2020 to June 2021. Data were collected from a total of 138 subjects (92 controls and 46 cases). Descriptive statistics was used to summarize the data, and logistic regression model was used to identify risk factors. The vaccine effectiveness (VE) was determined by computing the percentage reduction in risk of rabies among vaccinated humans relative to unvaccinated individuals. Majority of rabies exposure (56.5%) were due to bite of stray dogs or dogs owned by others. About 65.2% of the study subjects had taken PEV. Subjects with rabies PEV were less likely to have rabies than subjects who did not take rabies PEV (OR = 0.058, 95% CI = 0.001-0.21), and the rabies PEV reduced 94.2% of the rabies cases. Females, children <15 years of age, and increased number of days from bite to PEV had higher odds of deaths due to rabies. There was a considerable reduction in the odds of rabies case in vaccinated humans as compared to that of nonvaccinated subjects. By focusing on target populations such as females and children under the age of 15 and by capitalizing health education on early search of PEV following dog bite, the reduction level rabies-related death has the potential to be larger than the reported findings.