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A single dose of the Pfizer / BioNTech vaccine offers 92.6% efficacy in new calculations based on data submitted to the U.S. Food and Drug Administration (FDA), according to the researchers.
Together with previous findings that a single dose of Modern vaccine provides 92.1% efficacy against SARS-CoV-2 infection, the researchers propose that it is time to defer the second dose to extend protection to more people by single-dose mRNA vaccines.
Danuta M. Skowronski, MD, of the British Columbia Center for Disease Control in Vancouver, Canada, and Gaston De Serres, MD, PhD, of the National Institutes of Health of Quebec, Quebec, Canada, wrote a letter published on 17 February a The New England Journal of Medicine.
However, other experts disagree, saying more data is needed before deviating from the two-dose regimen evaluated in clinical trials. They also point out that the FDA granted an emergency use authorization based on the two-dose studies.
Following the studies
Dr. Dial Hewlett Jr.
“One of the things we have to keep in mind here is that when these vaccines are tested in clinical trials, they are tested in specific circumstances. In this case, two doses were used to achieve efficacy. The studies are not really done. they just gave it a dose and tried to go with it, “Dial Hewlett Jr., MD, medical director of the Westchester County Department of Health’s Disease Control Division in White Plains, New York, said today. an information session in the media, sponsored by infectious diseases. Society of America.
Dr. Matthew Zahn
Matthew Zahn, MD, who also spoke during the IDSA briefing, agreed. “The CDC has worked very hard to give an advantage to adherence to what is known science, and the trials examined two separate doses of vaccine for less than 6 weeks.
“That’s why we’ve kept that recommendation. From my side, I think it makes a lot of sense,” said Zahn, medical director of the Epidemiology and Evaluation Division of the Orange County Health Care Agency. , Santa Ana, California.
In their correspondence, the authors report that they examined the documents submitted to the FDA from two weeks after the first dose until the second vaccination. They note that “even before the second dose …[the vaccine] it was highly effective “.
Do two doses extend protection?
Even if the effectiveness of a dose exceeds 90% at first, how long this protection persists without a second dose remains an open question, said Hewlett, who is also a member of the National Medical Association COVID-19 Task Force on Vaccines and Therapeutics.
“We don’t have trial data indicating that vaccines will be just as effective if the time between the two doses is extended,” said Zahn, who also serves as the CDC Advisory Committee on Practical Liaison. of immunization.
Other researchers reported a 94.8% efficacy against SARS-CoV-2 after two doses of the Pfizer / BioNTech vaccine in a previous study. The same report estimated a single dose efficacy of 52.4% between the first and second dose, “but, in their calculation, they included data that were collected during the first two weeks after the first dose. , when immunity would have been further increased “. note Skowronski and De Serres.
“There may be uncertainty about the duration of protection with a single dose, but administering a second dose in one month after the first, as recommended, provides little added benefit in the short term, while people high-risk who might have received a first dose with this vaccine supply is left completely unprotected, ”they point out.
“It may be true that, in the short term, one dose may be effective,” Hewlett admitted, “but we don’t know how long this protection will last and the second dose will be added?” He explained that many public health officials want to simplify vaccine administration, but “before we can support that, we need to have data to analyze it.”
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, will certainly result in thousands of hospitalizations and deaths related to COVID -19 this winter in the United States: hospitalizations and deaths that would have been prevented with a first dose of vaccine. “
Skowronski has not revealed any relevant financial relationship. De Serres reported Pfizer support for an unrelated study of the seroprevalence of meningococcal antibodies.
N Eng J Med. Published online February 17, 2021. Correspondence
Damian McNamara is a staff Miami-based journalist. It covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.
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