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How fractional doses of COVID-19 vaccines could boost global supply by half a billion doses per month

An image of hands in blue gloves holding a syringe
Meyer & Meyer
A Dartmouth College economist is calling for testing of fractional COVID-19 doses to help boost global supply.

A group of the nation's leading economists published findings last month about how fractional doses of COVID vaccines could dramatically accelerate global vaccination rates by roughly half a billion doses per month.

Clinical evidence suggests that these smaller doses could also be highly effective against hospitalizations and severe disease resulting from COVID-19.

VPR’s Mitch Wertlieb spoke with one of the study's authors, Dartmouth College economics professor Christopher Snyder, about the recent findings. Their conversation below has been edited and condensed for clarity.

Mitch Wertlieb: Let me begin by asking about what fractional doses mean. I mean, why does this group feel that it's important to test them now? What do you mean by fractional doses?

Christopher Snyder: A fractional dose is taking the dose that was a standard dose as tested, according to initial clinical trials, and using less of the active ingredients. So for example, instead of using a certain number of milliliters for injection, you could say cut down half the active ingredient.

What you can do is you can take your existing capacity for producing vaccines, and you could double it, you know, if you're waiting for the vaccine because supplies are short, you can get it out twice as fast.

Is the strategy here potentially, that telling people that you're doing a fractional dose — in other words, giving them a dose of vaccine, but perhaps a little less potent, I guess, than a regular vaccine — would that get more people to want to take them that may be hesitant?

You know, you could imagine it going either way. And that's why you want to do some testing to assure people of efficacy. But possibly that would be a side benefit, is that if you can cut down the dose, you might not actually lose too much efficacy, but you might reduce side effects. And some of the initial testing that we've seen actually that result does seem to come through.

"What you can do is, you can take your existing capacity for producing vaccines, and you could double it, you know, if you're waiting for the vaccine because supplies are short, you can get it out twice as fast."
Christopher Snyder, Dartmouth College

One question I do have professor Snyder, too, is you know, why are a group of economists weighing in on what most people think of primarily as a health care issue?

I guess, in a sense, part of our value added here is people in the medical field are operating in a kind of business-as-usual mindset. And one of our main messages is to say that a pandemic is not a business-as-usual situation. Resources are short, and you might want to adjust what might be optimal, say, for what you do with, say, a childhood measles vaccine. Those protocols may not apply in a pandemic, because of the shortages that are invariably going to result.

Since you published the findings last month, have you heard from members of the medical community? Because we do know that, you know, even when it comes to things like boosters, and who should get them and how much, that there's still some disagreement, even among health care officials about this. What was their reaction when you published these findings?

Christopher Snyder sits with hands folded, wearing grey vest and white shirt.
Eli Burakian
Dartmouth, Courtesy
Christopher Snyder.

It takes a while to get things published, so we were certainly vetting it by all the leading medical people we could get in touch with and contact. We've been in contact also with, you know, the World Health Organization, and the Center for Emergency Preparedness Innovations.

And so, talking to them about possibly undertaking some of these trials, the reception has been remarkably positive. We're not necessarily advocating anyway that fractional doses be rolled out universally. If that's too radical of a move, we would certainly advocate testing.

Who do you think could benefit most from the testing of these fractional doses?

Supply constraints aren't such an issue now in high-income countries. Even if we need another booster, we'll have stockpiles for that. It's really the middle-income and low-income countries that are going to benefit the most, they still have very low rates of vaccination.

There's also problems with distribution, but part of the problem is scarce supplies, and if you can double supplies to middle and low-income countries, you can accelerate vaccinations there.

We undertook this study, you know, almost a year ago, and we've been vetting it by medical professionals. We've been talking to different agencies and governments. So, in a sense, it's driven policy even before it came out.

"It's really the middle-income and low-income countries that are going to benefit the most, they still have very low rates of vaccination."
Christopher Snyder, Dartmouth College

You said it took like a year to get just this research out and these findings. But not even talking about the next pandemic, we might still be in the next wave, if you will, because of BA.2 and things we don't know about this next variant of the [coronavirus]. So, in a sense, this timing could actually be very good.

You took the words out of my mouth. The next pandemic could be tomorrow. It could be a variant of COVID that our current vaccines don't work very well for. And so we might have to engineer, say, a new round of mRNA vaccines, and we're gonna have this incredible supply shortage, and we'll be back in the same situation we were a year ago. And so this information, this knowledge, this new protocol, could actually help in this pandemic with the next wave.

And professor Snyder, what do you know about the likelihood that any countries might be adopting this approach. Have any even started to dip their toes in, so to speak?

Yeah, some of my team is helping to organize some clinical trials in Nigeria that should be underway in a couple of weeks. It's a pretty advanced testing protocol. They are testing four different vaccines and three different dosages of those, and it's a large-scale trial, and they're going to see if we don't lose too much antibody protection.

Have questions, comments or tips? Send us a message or tweet Morning Edition host Mitch Wertlieb @mwertlieb.

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