Sixty seconds on . . . nasal vaccinesBMJ 2022; 377 doi: https://doi.org/10.1136/bmj.o1148 (Published 06 May 2022) Cite this as: BMJ 2022;377:o1148
Haven’t my nostrils been through enough?
Now, now. You must admit the nasal swab has proved invaluable in the pandemic. And it seems vaccine developers are interested in this orifice too. Trials on 12 potential nasal vaccine candidates against SARS-CoV-2 are currently underway.
What do we nose so far?
The covid-19 vaccines we use at the moment are all delivered through an intramuscular injection and have been shown to reduce severe illness and death. Nasal vaccines may be able to go a step further, however, by blocking infections completely at the site of entry. Plus, they would have the added bonus of needle free delivery.
Researchers at Lancaster University have developed one such nasal spray candidate, based on a poultry virus, and are now beginning human trials. During the preclinical phase, they reported that the spray “significantly reduced lung pathology, inflammation, and clinical disease” in rodents. Virologist Muhammad Munir said, “Our studies demonstrate that induction of a local immune response at the point of entry of SARS-CoV-2 has the potential not only to limit clinical disease but also—and perhaps even more importantly—virus transmission from infected to uninfected people.”1
Smells like teen spirit
The lack of needles means nasal sprays are often used in children and teenagers. However, their potential to block infection and even transmission means that, in the case of SARS-CoV-2, there could be benefit in rolling them out to a much wider population.
So what’s the blockage?
Nasal vaccines are quite tricky, especially as scientists do not know that much about mucosal immunity. In practice, ensuring that a person gets the right dose and doesn’t just sneeze out or swallow the vaccine can be troublesome, and from there the vaccine still needs to get past the mucus. Researchers also have to consider the closeness of the brain and ensure any vaccine does not cause neurological problems.
That’s a blow
It’s certainly not easy, but that doesn’t mean it’s impossible. Speaking at the Bill Gates book launch event this week, professor of vaccinology at Oxford University, Sarah Gilbert, who led development of the Oxford AstraZeneca covid-19 vaccine, sounded positive. “We have new technology coming through—for example, a spray you take up the nose. I’m hopeful about the advances made with the delivery of these mucosal delivery vaccines,” she said.