Nasel spray vaccines might stop the coronavirus in its tracks, although there’s little evidence from human trials so far.

China and India approve nasal COVID vaccines — are they a game changer? Nature - Scientists hope the immunizations, delivered through the nose or mouth, will prevent even mild cases of illness. Waltz, Emily nature

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These mucosal vaccines target thin mucous membranes that line the nose, mouth and lungs. By prompting immune responses where SARS-CoV-2 first enters the body, mucosal vaccines could, in theory, prevent even mild cases of illness and block transmission to other people — something COVID-19 shots have been unable to do. Vaccines that produce sterilizing immunity would be game changing for the pandemic. ...

Exactly how successful these vaccines will be is unclear. Expecting a vaccine to stop transmission of a virus or prevent even mild illness — achieving what is called sterilizing immunity — is a high bar. Bharat and CanSino won’t know whether their vaccines can achieve this until they have conducted further efficacy studies.

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