Many available vaccines have demonstrated post-exposure effectiveness, but no published systematic reviews have synthesized these findings. We searched the PubMed database for clinical trials and observational human studies concerning the post-exposure vaccination effects, targeting infections with an FDA-licensed vaccine plus dengue, hepatitis E, malaria, and tick borne encephalitis, which have licensed vaccines outside of the U.S. Studies concerning animal models, serologic testing, and

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... ne vaccines were excluded. Eligible studies were evaluated by definition of exposure, and their attempt at distinguishing pre- and post-exposure effects was rated on a scale of 1-4. We screened 4518 articles and ultimately identified 14 clinical trials and 31 observational studies for this review, amounting to 45 eligible articles spanning 7 of the 28 vaccine-preventable diseases. For secondary attack rate, this body of evidence found the following medians for post-exposure vaccination effectiveness: hepatitis A: 85% (IQR: 28; 5 sources), hepatitis B: 85% (IQR: 22; 5 sources), measles: 83% (IQR: 21; 8 sources), varicella: 67% (IQR: 48; 9 sources), smallpox: 45% (IQR: 39; 4 sources), and mumps: 38% (IQR: 7; 2 sources). For case fatality proportions resulting from rabies and smallpox, the vaccine efficacies had medians of 100% (IQR: 0; 6 sources) and 63% (IQR: 50; 8 sources) post-exposure. Although mainly used for preventive measures, many available vaccines can modify or preclude disease if administered after exposure. This post-exposure effectiveness could be important to consider during vaccine trials and while developing new vaccines.