They also rejected other ideas for expanding the vaccine supply, saying that people who speculate about the possibility of taking just one dose or reducing the dose in half misinterpret it.
“These are all reasonable questions to consider and evaluate in clinical trials. At present, the presentation of changes to the FDA-authorized dosage or schedules of these vaccines is premature and is not thoroughly rooted in the available evidence. Without appropriate data “In favor of such changes, in vaccine administration we run a significant risk to public health, undermining the historic vaccination efforts to protect the population against COVID-19,” they added.
Operation Warp Speed’s chief adviser, Moncef Slaoui, told CNN on Sunday that the FDA would consider giving half a dose of Moderna’s Covid-19 vaccine to people 18 to 55 – which could make the vaccine available to twice as many people. in this age group.
Slaoui said earlier data showed the vaccine appeared to elicit effective antibody responses among volunteers younger than 55 who received the full dose of 100 micrograms or a half dose. An FDA information document also referred to these “comparable” immune responses from Moderna’s Phase 2 study last month, but the full data have not yet been published.
But Marks and Hahn said these findings only cover a few people who were not followed for long to see if their immune responses persisted over time.
“What we have seen is that the data in the companies’ submissions on the first dose are generally misinterpreted. In Phase 3 trials, 98% of the participants in the Pfizer-BioNTech trial and 92% of the participants in the Moderna trial received two doses of the vaccine at three- or four-week intervals, respectively, ‘they wrote.
‘Participants who did not receive two vaccines with an interval of three or four weeks were generally only followed for a short time, so that we can not definitively determine the depth or duration of protection after a single dose of vaccine from the single dose percentages reported by the companies. ‘
British officials have said they will take more than 21 days between doses of Pfizer’s vaccines, and will consider allowing people to be vaccinated with two different vaccines. Hahn and Marks rejected these ideas for the US.
“The available data still support the use of two specified doses of each authorized vaccine at specified intervals. For the Pfizer / BioNTech COVID-19 vaccine, the interval is 21 days between the first and second dose. And for the Modern COVID-19 vaccine , the interval between the first and second dose is 28 days, ”they wrote.
It is understandable that people want to stretch the vaccine supply, they said. But it is not advisable.
“If people do not really know how protective a vaccine is, damage can occur because they can assume that they are fully protected if they do not, and therefore change their behavior to take unnecessary risks,” he said. they said.
Dr. Paul Offit, an infectious disease specialist at the University of Pennsylvania, told CNN he thinks it’s a bad idea to halve the dose of the vaccine.
“There is no data on the efficacy of half a dose. If you use half a dose, just make it up. You just hope you’m right,” said Offit, a member of the FDA’s vaccinations and related biological drugs, added. Products Advisory Committee. “Why would you dare make something up if you do not know if it works?”
Dr. Arnold Monto, who acted as chairman of the committee last month during meetings to consider Moderna and Pfizer’s vaccination applications, told CNN on Monday that the dose reduction would be extraordinary. “It would be a very unusual step, given the fact that it was not studied in Phase 3, but emergencies are also a very unusual step,” said Monto, a professor of epidemiology at the University of Michigan.
Dr Sanjay Gupta and Elizabeth Cohen of CNN contributed to this story