Vaccines work by stimulating the body to produce a high-quality, rapid and specific immune response upon exposure to infection by a particular disease-causing microorganism - the microorganism targeted by the vaccine. Evidence is emerging that some vaccines may have additional 'non-specific effects' (NSEs); that is, effects on the immune system beyond the direct protection against the diseases for which the vaccines were developed. It has been proposed that rabies vaccine has protective NSEs in people and animals, with receipt of rabies vaccine in children associated with a reduced risk of meningitis and cerebral malaria in one study, and a history of rabies vaccination in free-roaming dogs associated with increased survival rates in another study. Studies in mice have shown that prior rabies vaccination protects against bacterial sepsis. The biological mechanism of action of any such NSE of rabies vaccine is unknown. Other vaccines with reported protective NSEs (e.g. bacillus Calmette-Guerin vaccine against tuberculosis, a disease caused by Mycobacterium tuberculosis) have been show to reprogram the immune system, leading to enhanced protection against infection with disease-causing microorganisms unrelated to M. tuberculosis. In this study, we will test the hypothesis that rabies vaccine has non-specific protective effects against common infectious disease (CID) syndromes (upper respiratory illness, diarrhea and fever) in a population of veterinary students. We will randomly assign previously-unvaccinated students who volunteer for the study to receive a primary course of three injections of rabies vaccine (experimental group) or an identical course of three injections of sterile water (control group). Participants will not know to which group they have been assigned. We will ask all participants to report episodes of illness through an online survey each week for 26 weeks, and will also record all clinically- and laboratory-confirmed cases of illness with CID syndromes. We hypothesize that rates of self-reported new episodes of CID illness over 26 weeks will be at least 25% lower in the experimental group, relative to the control group.
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Number of self-reported new episodes of acute common infectious disease (CID), defined as any of the following: upper respiratory illness (URI) or influenza-like illness (ILI) or diarrhea (DIA) or undifferentiated febrile illness (UFI)
Timeframe: Weekly self-reporting of occurrence or non-occurrence of episodes of CID for a maximum of 26 weeks, starting one week after allocation