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He later clarified in a second tweet that he was not recommending that this was 100% the way forward, but that it was worth “giving states the flexibility to try it”.
Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN’s Erin Burnett on Wednesday that Adams’ tweets did not take into account the impact of the virus variants, which may decrease the level of vaccine protection.
“First of all, I love Jerome Adams. He’s a really great guy. We worked so well together during the Trump administration,” Fauci said. “I think he’s wrong about that.”
By using only one dose, “you are at a very low level. Good enough to provide protection, but if you lower it five times, you fall off the protection card.”
The use of mRNA vaccines has been approved in the United States based on clinical trial data which shows that two doses of the vaccine taken a few weeks apart are approximately 95% effective in preventing symptomatic infection. Clinical trials for both vaccines show that the second dose gives protective antibodies a big boost.
DC guidelines continue to advise two doses of the Pfizer and Moderna vaccines, and experts at the CDC Advisory Committee on Immunization Practices (ACIP) meeting on Monday said there was not enough scientific evidence to support a vaccination strategy that would delay a second dose or eliminate it all. together.
“Five studies have shown that postponing the second dose of mRNA may leave some people less protected against the SARS-Cov-2 variants,” CDC’s Dr Heather Scobie said at the ACIP meeting.
That’s not to say that there won’t be more dosage changes to come.
Around the world, researchers are studying the effectiveness of single doses of mRNA vaccines. Meanwhile, the J&J vaccine – currently licensed as a single-dose vaccine – is also being tested in two doses to see if it will offer more protection.
Study single doses
Since late December, the UK has not told people to skip the second shot, but has delayed second doses of the Pfizer / BioNTech vaccine to prioritize first doses. The delay meant that the interval between doses could be extended up to 12 weeks instead of about three.
In reaction to the change in the vaccination schedule, Pfizer said at the time that it had not tested its vaccine this way.
“Pfizer and BioNTech’s Phase 3 study for the Covid-19 vaccine was designed to assess the safety and efficacy of the vaccine on a 2-dose schedule, separated by 21 days,” Pfizer said. “There is no data to show that protection after the first dose is maintained after 21 days.”
Researchers at Israel’s largest hospital looked at what happened after 7,000 staff were vaccinated with the first dose of the Pfizer / BioNTech vaccine. From the second to the fourth week after receiving the first vaccine, symptomatic infection rates were down 85%.
Some research also suggests that one dose may be enough for people who have had an infection in the past. Two articles published last week in The Lancet found that a single dose of Pfizer / BioNTech’s coronavirus vaccine can induce a sufficiently strong immune response in people who have previously had the coronavirus that it could protect from infection. future. France has already recommended that people previously infected receive a single dose.
In a letter sent to the New England Journal of Medicine in February, Canadian researchers scanned the documents Pfizer / BioNTech submitted for emergency use authorization last year and concluded that a single dose is still at least 90% effective.
“With such a highly protective first dose, the benefits derived from a limited vaccine supply could be maximized by postponing the second doses until all members of the priority group are offered at least one dose,” they said. added.
But, they noted that it’s still unclear how long protection lasts with a single dose.
CNN’s Lauren Mascarenhas and Maggie Fox contributed to this report.
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