RACHEL MARTIN, HOST:
The goal of a COVID-19 vaccine is to prevent people from getting very sick. It's also important to prevent the spread of the disease. But many vaccines currently being developed don't seem to be able to do that. There are some scientists, though, that think a vaccine in the form of a nasal spray could solve the problem. NPR science correspondent Joe Palca explains.
JOE PALCA, BYLINE: Most vaccines are given as a shot in the arm - the deltoid muscle, to be precise. And for the COVID-19 vaccines under development, it's the same.
FRANCES LUND: The majority of vaccines - in fact, all of the ones that are currently in clinical trials - are delivered via the muscle.
PALCA: Frances Lund is an immunologist at the University of Alabama, Birmingham.
LUND: You will get a systemic response, but you will not get a local response with that.
PALCA: By systemic response, Lund is talking about generating antibodies that circulate through the blood to all parts of our bodies. This is good. But for a respiratory virus like a coronavirus, the infection typically starts in the nose or throat, and an infection can take hold there before the systemic immunity kicks in. The vaccine might protect you from getting sick, but you still might have virus in your nose that you could spread to others. Lund says by putting a vaccine directly into the nose, you could get another kind of immunity that occurs primarily in the cells lining the nose and throat.
LUND: You still get systemic immunity if you deliver it via the intranasal route, so that doesn't go away. And you add a level of immunity that you don't get with the intramuscular vaccine, and that immunity is local.
PALCA: So the systemic immunity will keep you from getting sick, and the local immunity means it'll be harder for the virus to get a foothold in your nose, if you'll forgive the mixed metaphor. Lund is working with a company called Altimmune to make such a vaccine.
Now, you may be thinking, hang on - if we get a vaccine that totally prevents you from getting sick, what does it matter if you can infect others? The vaccine would protect them, too. At least, I was wondering that.
MICHAEL DIAMOND: That's absolutely good logic.
PALCA: Michael Diamond is at Washington University. The logic may be good, he says, but there's a practical issue. At least at first, there won't be enough vaccine for everyone.
DIAMOND: Even if we had adequate supplies of vaccines, there are two problems. One, some people are not going to take a vaccine.
PALCA: Surveys say that's true.
DIAMOND: And then there's a fragment of the population which just won't mount good responses to a vaccine.
PALCA: Meaning they may not make antibodies that will protect them - a vaccine that prevents virus spread is desirable but not always feasible. Diamond is working on a vaccine administered to the nose which he describes in the journal Cell. Although not common, Diamond says spray vaccines are out there.
DIAMOND: There's already a flu vaccine called FluMist which is used now. And so we expect that the similar technology that's used for existing nasal spray vaccines would be able to be applied to this one.
PALCA: Complete protection, no infecting others and no needles - seems like an idea worth pursuing.
Joe Palca, NPR News.
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