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A single dose of Pfizer / BioNTech vaccine provides 92.6% efficacy in new calculations based on data submitted to the US Food and Drug Administration (FDA), the 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 dose mRNA vaccinations. unique.
Danuta M. Skowronski, MD, of the British Columbia Center for Disease Control in Vancouver, Canada, and Gaston De Serres, MD, Ph.D., of the Quebec National Institutes of Health, Quebec City, Canada, wrote a letter published on February 17 in The New England Journal of Medicine.
However, other experts disagree, saying more data is needed before deviating from the two-dose regimen assessed in clinical trials. They also point out that the FDA has granted emergency use authorization based on two-dose studies.
Respecting studies
Dr. Dial Hewlett Jr.
“One of the things we should consider 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 didn’t just focus on one dose and try to go with just that, “Dial Hewlett Jr., MD, medical director of the Division of Disease Control at Westchester County Department of Health in White Plains, New York, said today during a media briefing, sponsored by the Infectious Diseases Society of America.
Dr. Matthew Zahn
Matthew Zahn, MD, who also spoke during the IDSA briefing, agreed. “The CDC has worked hard to give a first adherence to what is known science, and studies have looked at two separate doses of vaccine less than 6 weeks apart.
“That’s why I kept this recommendation. For my part, I think that makes a lot of sense,” said Zahn, medical director in the Division of Epidemiology and Evaluation, Orange County Health Care Agency, Santa Ana, California.
In their correspondence, the authors report that they have examined documents submitted to the FDA from 2 weeks after the first dose until the second immunization. They note that “just before the second dose …[the vaccine] it was extremely effective. “
Do two doses extend protection?
Even if the effectiveness of a dose exceeds 90% in the beginning, how long that protection lasts without the 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 data on studies that say vaccines will be as effective if you extend the time between the two doses,” said Zahn, who also serves as a liaison to the CDC’s Advisory Committee on Immunization Practices.
Other researchers reported a 94.8% efficacy against SARS-CoV-2 after two doses of 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 included in their calculation data that were collected in the first 2 weeks after the first dose, when immunity would have increased further.” notes Skowronski and De Serres.
“There may be uncertainty about the duration of single-dose protection, but administering a second dose within one month after the first, as recommended, offers few added benefits in the short term, while high-risk individuals who would being able to receive a first dose with this vaccine is left completely unprotected, “they note.
“It may be true that, in the short term, one dose may be effective,” Hewlett acknowledged, “but we don’t know how long this protection will last and a second dose will be added to that?” He explained that many public health officials want to simplify the administration of the vaccine, but “before we can support this, we will need data to analyze this.”
Skowronski and De Serres conclude their letter by stating that “given the current lack of vaccine, postponing the second dose is a matter of national security which, if ignored, will certainly lead to 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 did not disclose any relevant financial statements. De Serres reported Pfizer’s support for a study unrelated to the seroprevalence of meningococcal antibodies.
N Eng J Med. Published online February 17, 2021. Correspondence
Damian McNamara it’s 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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