As per Dr Krishna Ella, Chairman and MD, Bharat Biotech, one of the reasons the company has greenlighted speedier trials and clinical study of its experimental nasal vaccine is for possible use as a booster shot. As per developers, the use and effectiveness of nasal vaccines, right now, when we have other vaccines in use is being studied as a standalone vaccine, but also as a booster shot. For example, Bharat Biotech is currently leading with trials of using its nasal vaccine dose as a follow-up to its two-dose intramuscular vaccine, Covaxin. Doing so, according to experts would prime the innate immunity in the body (via administration of two doses of Covaxin) and consequently, boost the mucosal immunity (present in the nose) as well as strengthen the iGG and IgA antibody immunity, which would protect against infection and cut chances of contracting the viral bug.
Similar approaches are also being tried out by other companies with their nasal vaccines. Certain studies done in Britain, for example, have also highlighted that nasal vaccine doses could effectively dole out a stronger and manyfold effective antibody response against the virus.
Now, while booster and additional shots of the COVID-19 vaccine are currently under review, and strongly advised for those who may be immunocompromised are a long shot, having nasal vaccine doses could cover up the issues, and make other intramuscular vaccines available for those who may need it more since a lot of countries are still in short supply. While more research is needed to back preliminary findings, nasal vaccines may also provide strengthened immune and antibody response, which may wane after vaccination.