SCIENTISTS DEBATE DOSE DISTRIBUTION
Some suggest wider rollout of just 1 shot instead of 2 shots
As governments around the world rush to vaccinate their citizens against the surging coronavirus, scientists are locked in a heated debate over a surprising question: Is it wisest to hold back the second doses everyone will need, or to give as many people as possible an inoculation now — and push back the second doses until later?
Since even the first shot appears to provide some protection against COVID-19, some experts believe that the shortest route to containing the virus is to disseminate the initial injections as widely as possible now.
Officials in Britain have already elected to delay second doses of vaccines made by the pharmaceutical companies AstraZeneca and Pfizer as a way of more widely distributing the partial protection afforded by a single shot.
Health officials in the United States have been adamantly opposed to the idea. “I would not be in favor of that,” Dr. Anthony Fauci, the nation’s top infectious disease expert, told CNN on Friday. “We’re going to keep doing what we’re doing.”
But on Sunday, Moncef Slaoui, scientific adviser of Operation Warp Speed, the federal effort to accelerate vaccine development and distribution, offered up an intriguing alternative: giving some Americans two half-doses of the Moderna vaccine, a way to possibly milk more immunity from the nation’s limited vaccine supply.
The rising debate ref lects nationwide frustration that so few Americans have gotten the first doses — far below the number the Trump administration had hoped would be inoculated by the end of 2020. But the controversy itself carries risks in a country where health measures have been politicized and many remain hesitant to take the vaccine.
“Even the appearance of tinkering has negatives, in terms of people having trust in the process,” said Natalie Dean, a biostatistician at the University of Florida.
The vaccines authorized so far in the United States are produced by PfizerBioNTech and Moderna. Britain has greenlit the Pfizer-BioNTech and Oxford-AstraZeneca vaccines.
All of them are intended to be delivered in multiple doses on a strict schedule, relying on a tiered protection strategy. The first injection teaches the immune system to recognize a new pathogen by showing it a harmless version of some of the virus’ most salient features.
After the body has had time to study up on this material, as it were, a second shot presents these features again, helping immune cells commit the lesson to memory. These subsequent doses are intended to increase the potency and durability of immunity.
Clinical trials run by Pfizer-BioNTech and Moderna showed the vaccines were highly effective at preventing cases of COVID-19 when delivered in two doses separated by three or four weeks.
Some protection appears to kick in after the first shot of vaccine, although it’s unclear how quickly it might wane. Still, some experts now argue that spreading vaccines more thinly across a population by concentrating on first doses might save more lives than making sure half as many individuals receive both doses on schedule.