Post-exposure prophylactic vaccine candidates for the treatment of human Risk Group 4 pathogen infections

INTRODUCTION: The development of therapeutics and vaccines to combat Risk Group 4 pathogens, which are associated with high case-fatality rates, is a high priority. Post-exposure prophylactic vaccines have the potential to bridge classical therapeutic and vaccine applications, but little progress has been reported to date. AREAS COVERED: This review provides an overview of post-exposure prophylactic vaccine candidates against Risk Group 4 pathogens. EXPERT OPINION: A few candidate post-exposure prophylactic vaccines protect experimental animals infected with a few Risk Group 4 pathogens, such as filoviruses or hantaviruses, but efficacy of candidate vaccines has not been similarly reported for most other high-consequence pathogens. A major drawback for the further development of existing candidates is the lack of understanding of their mechanisms of action, knowledge of which could help to identify focused paths forward in vaccine development and licensure. These drawbacks to further development ultimately slow progress toward post-exposure prophylactic vaccine licensure.