Protection against SARS-CoV-2 transmission by a parenteral prime-Intranasal boost vaccine strategy.

Background: Licensed vaccines against SARS-CoV-2 effectively protect against severe disease, but display incomplete protection against virus transmission. Mucosal vaccines providing immune responses in the upper airways are one strategy to protect against transmission.

Methods: We administered Spike HexaPro trimer formulated in a cationic liposomal adjuvant as a parenteral (subcutaneous - s.