Making Sense of Medical Science (MSMS)

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A November 5 preprint showed that a nasal spray was 100% effective in preventing infection in an animal CoV-2 infection model. The spray contained a small piece of the SARS-CoV-2 spike protein designed to block the ability of the virus to enter human cells in the respiratory tract.

Ferrets were given the nasal spray and then placed in cages with an infected partner to see if the virus would transfer to the treated animal. After 24 hours, 100% of the animals that received a sham spray were infected while none of the animals that received the experimental nasal spray were infected. This not only shows that the spray seems to work, it also confirms that sinus exposure to the virus is the primary route of infection–at least in ferrets. It shows that saliva exchange, sharing food and water, etc., are not as important routes of infection.

While very encouraging, this also is very preliminary. We need to learn how long such protection lasts, whether it works early after infection, whether it works in humans, and assess its safety profile in humans.

Such a pre-exposure, or even early post-exposure prophylactic, would be very helpful to high risk people, front-line health care workers, teachers, nursing home residents, and many others. If it works, it could provide a relatively inexpensive and readily available prophylaxis and complement the vaccines that will likely be soon approved. Since it seems that only about 50% of the US are willing to get an anti-CoV-2 vaccine, which is not sufficient to confer herd immunity, a preventive measure like this nasal spray could go a long way in reducing the R₀ value for CoV-2 to <1.