New data spurs calls for single dose of COVID-19 vaccine

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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), researchers report.

Along with previous findings that a single dose of Moderna vaccine provides 92.1% efficacy against SARS-CoV-2 infection, researchers suggest it is time to postpone the second dose to extend protection to more people through 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 Institut national de la santé du Québec, Quebec, Canada, wrote a letter published on 17 February in The New England Journal of Medicine.

Other experts disagree, however, saying more data is needed before turning away from the two-dose regimen being evaluated in clinical trials. They also point out that the FDA granted emergency use authorization based on the two-dose studies.

Stick to studies

“One of the things we have to 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 weren’t actually aimed at. to give one, ”Dial Hewlett Jr, MD, medical director of the Westchester County Department of Health’s Disease Control Division in White Plains, New York, said today during a press briefing , sponsored by the Infectious Diseases Society of America.

Matthew Zahn, MD, who also spoke at the IDSA briefing, agreed. “The CDC has worked very hard to emphasize sticking to what is known about science, and the trials have looked at two doses of the vaccine separated by less than 6 weeks.

“This is really why we have maintained this recommendation. From my side, I think that makes a lot of sense, ”said Zahn, medical director of the Division of Epidemiology and Assessment, Orange County Health Care Agency, Santa Ana, Calif.

In their correspondence, the authors report reviewing 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 efficient. “

Do two doses extend protection?

Even if the effectiveness of one dose exceeds 90% initially, how long that protection persists without a second dose is still an open question, said Hewlett, who is also a member of the National Medical Association’s COVID-19 working group. on vaccines and therapeutics.

“We have no test data to indicate that vaccines will be equally effective if you lengthen the time between doses,” said Zahn, who also serves as the liaison representative to the CDC’s Advisory Committee on Immunization Practices. .

Other researchers reported 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 was collected in the first 2 weeks after the first dose, so that immunity would have increased further “. note Skowronski and De Serres.

“There may be uncertainty about the duration of protection with a single dose, but giving a second dose within one month of the first, as recommended, provides little benefit. additional short-term, while high-risk people who might have received a first dose with this vaccine supply are left completely unprotected, ”they note.

“It may be true that in the short term one dose could be effective,” Hewlett conceded, “but we don’t know how long that protection will last, and will the second dose add to that? ” He explained that many public health officials wanted to simplify the administration of vaccines, but “before we can support this we are going to have to have data on this.”

Skowronski and De Serres conclude their letter by stating that “given the current shortage of vaccines, postponing the second dose is a matter of national security which, if ignored, will certainly result in thousands of hospitalizations and deaths linked to COVID-19 this winter in the United States – hospitalizations and deaths that would have been prevented with a first dose of the vaccine. “

Skowronski did not disclose any relevant financial relationship. De Serres reported a grant from Pfizer for an independent study of the seroprevalence of antibodies against meningococcus.

N Eng J Med. Published online February 17, 2021. Correspondence

Damian mcnamara is a stick Miami-based reporter. It covers a wide range of medical specialties, including infectious diseases, gastroenterology and intensive care. Follow Damian on Twitter: @MedReporter.

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