As the world amasses experience with COVID-19 vaccines, something we should have known from the start is coming into sharp focus.
Vaccines that are injected into arm muscles aren’t likely to be able to protect our nasal passages from marauding SARS-CoV-2 viruses for very long, even if they are doing a terrific job protecting lungs from the virus. If we want vaccines that protect our upper respiratory tracts, we may need products that are administered in the nose — intranasal vaccines.
Can they be made? Probably. Will they do what we want them to do, if they are made? Possibly. Is there still room for this type of next-generation product, given the record number of COVID vaccines that have already been put into use? Potentially. Will it be difficult to get them through development? Likely.
Some immunology basics would be helpful to understand the issues at stake here.
SARS-2 attacks us via the respiratory tract, with the resulting infections causing no symptoms in some people, mild to moderate cold and flu-like symptoms in others, and severe, life-threatening illness in the lungs of others.
Vaccines that are injected into the arm have done a spectacular job at preventing severe disease and death. But they do not generate the kind of protection in the nasal passages that would be needed to block all infection. That’s called “sterilizing immunity.”
There’s no reason to believe that intranasal vaccines would block all infection either, but experts say they could do a better job than existing vaccines, by better protecting mucus membranes of the nose and throat. (STAT)
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