Safe Sniff

Another Booster. It looks like those of us who were first in line for COVID-19 vaccine booster shots last summer (over 65 or immunocompromised) will need to get another booster sometime soon. The CDC reports that protection against the Omicron variant begins to wane after 4-5 months, which is right now if you got the booster shot last August or September. The CDC has not issued guidance (as of this writing) for getting another booster shot with the Pfizer or Moderna mRNA vaccines, but that is likely to be the only option available for the next few months.


Intranasal Vaccines. Preclinical studies of intranasal COVID vaccines in animals have resulted in robust protection against infection, resulting in the start of clinical trials in humans with several candidate vaccines. The advantage of nasal spray vaccines is that they induce strong mucosal immunity at the site where the coronavirus first enters the body, with the possibility that they can actually prevent infection (as in the animal model studies). The current vaccines are all given by intramuscular injection, resulting in a strong antibody and cellular immune response, but less effective mucosal immunity. As such, they are good at preventing or reducing serious illness or death, but are not expected to prevent infection, as we have just learned from the spike in Omicron infections in vaccinated individuals. Intranasal vaccines have some other advantages; e.g. they are easier to store and administer, and they are more acceptable to those who don’t like getting needles stuck in their arms.


The intranasal vaccines in clinical trials differ from the mRNA Pfizer or Moderna vaccines and are more similar to the Johnson & Johnson vaccines in that they use attenuated virus particles to deliver the COVID virus spike proteins to the cells lining the upper respiratory tract. An alternative approach is to coat very small nanoparticles with the spike proteins which are then ingested by the respiratory mucosal cells. Both approaches work well in preclinical models, and both are being evaluated in clinical trials. Results from these trials are not expected until the end of this year.


Will intramuscular or intranasal vaccine boosters be necessary if the current Omicron infection rate continues to drop? The answer is unfortunately yes, because COVID-19 variants will continue to arise in the many unvaccinated individuals in the U.S. (only 65% of U.S. residents are fully vaccinated, ranking us 58th in the world) and in the developing countries with even lower vaccination rates. Most experts now predict that the COVID-19 coronavirus will become an endemic infection with waves of recurrence like influenza. If this prediction holds up, an intranasal vaccine that prevents infection will be a very important addition to the ongoing fight against the disease that has now killed more than 900,000 of our fellow citizens