The prospect would effectively double the number of vaccine doses available and allow more people to be vaccinated quickly. But the idea sparked debate, with experts saying there was not yet enough evidence to justify a single dose and people should plan to receive two.
Pressure to explore the idea of a single-dose vaccine crystallized with a recent New York Times editorial by Michael Mina, an immunologist at Harvard TH Chan School of Public Health, and Zeynep Tufecki , a sociologist who has written extensively on the pandemic.
They called for the immediate launch of a new clinical trial to determine whether one dose of the vaccine is sufficient. They cited data from previous trials for Pfizer and Moderna vaccines which showed protection began after the first dose, with up to about 90% effectiveness, compared to about 95% after two doses.
There are questions about how long the protection will last without the second booster dose, but Mina and Tufecki wrote that the possibility of needing a single dose should be investigated immediately.
“If so, it would be a game-changer, allowing us to immunize up to twice as many people and significantly alleviate suffering not only in the United States, but also in countries where vaccine shortages can take a toll. years. solve, ”they wrote.
Part of the question is how aggressive it is to go ahead with a single dose which might be a little less effective than two doses, but would extend protection to twice as many people at one time. where on average about 2,500 Americans die from the virus each day and vaccines are not on track to be widely available for months.
“What can we do now so that in one month we haven’t had 60,000 deaths?” said Christopher Gill, professor of global health at the Boston University School of Public Health. He said there should at least be a debate about immediately vaccinating twice as many people with a single dose, without waiting for another trial.
“If you wait, you could be dead,” he said.
Scott Gottlieb, a former Food and Drug Administration (FDA) commissioner, questioned the administration’s strategy of withholding half of the doses to ensure there are enough for everyone to receive their second dose, since in the worst-case scenario only one dose is still at least partially as good.
The administration withholds 2.9 million doses to serve as a second dose for the 2.9 million people vaccinated in the first week rather than deploying all the doses at the same time, he told me Assistant Secretary of Health and Social Services Brett Giroir.
“We know the first dose is partially protective, the data is now available, so you want to try and distribute as many doses as possible to give as many people as possible benefits,” Gottlieb, who is now a board member. directors of Pfizer, said on CNBC earlier this month.
Other experts, including those at Operation Warp Speed and the FDA, are pushing back those who point to a dose, noting that months of careful study have been conducted on the two-dose regimen.
“The second dose is an integral part of the label if the vaccines are approved,” Moncef Slaoui, chief scientific adviser for Operation Warp Speed, said at a press briefing. “It bolsters patients’ immunity to COVID-19, and this is the data that shows lasting immunity, at least over a few months. And I expect it to be very durable. Therefore, people should not take the vaccine as a single dose vaccine. ”
However, he left the door open to further his studies. “One might ask the question, why not conduct efficacy trials with a single-dose vaccine of the Moderna vaccine or the Pfizer vaccine?” he added. “It would be a valid question. Of course, the timing would be a big challenge. ”
Peter Marks, the official FDA official who oversees the vaccine review, noted in a separate press conference that the trials and reviews were based on two doses.
“We have spent so much time carefully reviewing the data and basing our decisions on science, that it seems rather unwise to assume that a dose might be acceptable without knowing it,” he said.
Mina, the Harvard professor, said the United States would have to hold a retrial to find out for sure, which he said would take two to three months.
“Even if it’s slightly lower, from a public health point of view, it could be higher,” he said of one dose, meaning that a slightly less effective vaccine split over two times more people would help reduce the overall spread of the virus faster.
Moderna said he had no plans for a retrial, however.
“We have only studied a two-dose regimen and believe it is very effective in all age groups with an expectation of sustainability,” said a spokesperson for Moderna. “We are not currently planning to study a single dose regimen.”
In the meantime, Eric Topol, professor of molecular medicine at Scripps Research, said it was important to inform people that they should be given two doses until more is known.
“The points for studying this are good, but the public message to many to skip the 2nd dose is troubling when we don’t really know what protection it provides,” he tweeted.
There is also another vaccine in the works, from Johnson & Johnson, which may have results from its phase three trial early next year. The vaccine only uses one dose.