Next-Generation Coronavirus Disease 2019 Vaccines: Clinical Data and Future Directions.

Current coronavirus disease 2019 (COVID-19) vaccines have prevented millions of deaths since the beginning of the pandemic. Yet, current vaccines have critical limitations: (1) they elicit poor mucosal immune responses with reduced protection against infection and viral transmission, (2) immune responses wane quickly, and (3) new immune evasive severe acute respiratory syndrome coronavirus 2 variants continue to emerge. Next-generation vaccines aim to induce improved mucosal immunity via mucosal administration, and to elicit a greater duration and breadth of immune responses through new platforms like self-amplifying RNA. This review focuses on next-generation COVID-19 vaccines that have publicly available clinical data and are most likely to proceed in further development.