Introduction
infections, respiratory mucosal SARS-CoV-2 vaccine
DISEASE, INFECTIONS
SARS-CoV-2 omicron sublineages have shown a strong ability to evade neutralising antibodies because of their continuous evolution.Although evidence indicates that a booster dose of existing SARS-CoV-2 vaccines provides sustained protection against severe disease or hospitalisation caused by omicron variants, the effectiveness against symptomatic infections rapidly wanes within 3–6 months of vaccination for the primary series and booster dose.The development of mucosal SARS-CoV-2 vaccines has been the subject of intense focus, owing to the advantage of inducing local immunity in the respiratory tract faster than effectors present in peripheral circulation.In December, 2022, dNS1-RBD obtained emergency use authorisation in China. We aimed to assess the safety and efficacy (but not the immunogenicity) of dNS1-RBD against COVID-19, representing a breakthrough in respiratory mucosal SARS-CoV-2 vaccine research.