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A single dose of Pfizer / BioNTech vaccine offers 92.6% efficiency in new calculations, based on data submitted to the US Food and Drug Administration (FDA), researchers report.
Together with previous findings that a single dose of Moderna vaccine provides 92.1% efficacy against SARS-CoV-2 infection, investigators suggest it is time to postpone the second dose to extend protection to more people by single-dose mRNA vaccinations.
Danuta M. Skowronski, MD, of the British Columbia Center for Disease Control in Vancouver, Canada, and Gaston De Serres, MD, PhD, of the Quebec National Institutes of Health, Quebec City, Canada, wrote a paper that on 17 February in The New England Journal of Medicine.
Other experts disagree, saying more information is needed before being diverted from the two-dose regimen evaluated in clinical trials. They also point out that the FDA has granted permission for emergency use based on the two-dose studies.
Stick to the studies
Dr. Dial Hewlett Jr.
“One of the things we need to consider here is that when these vaccines are tested in clinical trials, they are tested under specific conditions. In this case, two doses were used to achieve efficacy. The studies did not actually look at the give one non-dose and try to go along with it, “said Dial Hewlett Jr., medical director of the Disease Control Division at the Westchester County Department of Health in White Plains, New York, today during a media conference sponsored by the Infectious Diseases. Society of America.
Dr Matthew Zahn
Matthew Zahn, MD, who also spoke at the IDSA briefing, agreed. “The CDC worked very hard to give a premium to compliance with the known science, and the trials looked at two vaccine doses separated by less than 6 weeks.
“That’s really why we kept the recommendation. For my part, I think it makes a lot of sense,” said Zahn, medical director of the Division of Epidemiology and Assessment, Orange County Health Care Agency, Santa Ana, California. .
In their correspondence, the authors report that they examined documents submitted to the FDA from 2 weeks after the first dose until the second vaccination. They note that “even before the second dose …[the vaccine] was very effective. ‘
Does two doses of protection extend?
Even if the efficacy of one dose first exceeds 90%, protection without a second dose remains an open question, says Hewlett, who is also a member of the National Medical Association COVID-19 Task Force on Vaccines and Therapeutics.
“We have no trial data that say the vaccines will be as effective as extending the time between the two doses,” Zahn said. He also serves as liaison representative to the CDC’s Advisory Committee on Immunization Practices.
Other researchers reported an efficacy of 94.8% against SARS-CoV-2 after two doses of Pfizer / BioNTech vaccine in a previous study. The same report estimates a single dose of 52.4% efficacy between the first and second doses, “but in their calculation they included data collected during the first two weeks after the first dose, when immunity would still increase. , “note Skowronski and De Serres.
“There may be uncertainty about the duration of protection with a single dose, but the administration of a second dose within 1 month after the first, as recommended, offers little additional benefit in the short term, while high-risk individuals taking a first dose with the vaccine supply is left completely unprotected, ‘they note.
“It’s true that one dose can be effective in the short term,” Hewlett admitted, “but we do not know how long this protection will last, and will the second dose contribute to it?” He explained that many public health officials wanted to simplify the administration of vaccines, but “before we can support them, we will need data that looks at this.”
Skowronski and De Serres conclude their letter by stating that ‘given the current shortage of vaccines, the postponement of the second dose is a matter of national security which, if ignored, would certainly result in thousands of COVID-19-related hospitalizations and deaths. this winter in the United States – hospitalizations and deaths that would be prevented with a first dose of vaccine. ‘
Skowronski did not disclose any relevant financial matters. De Serres reported that Pfizer is supporting an unrelated study of serocrevalence of meningococcal antibodies.
N Eng J Med. Published online on February 17, 2021. Correspondence
Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology and critical care. Follow Damian on Twitter: @MedReporter.
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