(CNN) – The United States is committed to its strategy of administering two doses of the Moderna and Pfizer / BioNTech Covid-19 vaccines a few weeks apart. Still, the idea of expanding the offering by delivering just one dose has not faded.
The Trump administration’s surgeon general, Dr. Jerome Adams, said in a statement tweet on Tuesdayy that the good protection available with one shot is “better than good protection for a few.”
He later clarified with a second tweet that he did not recommend that it was 100% the right way, but that it was worth it to “ give states the flexibility to try it. ”
Although 80.5 million vaccine doses have been administered in the United States and the single-dose Johnson & Johnson vaccine is entering the U.S. supply, demand still outstrips the number of vaccines available.
That hasn’t prompted vaccine makers, the U.S. Food and Drug Administration, or the CDC to switch to single doses to cover more people sooner.
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 virus variants, which can reduce levels of protection against vaccines.
“First of all, I love Jerome Adams. He’s a really great guy. We worked so well together during the Trump administration, ”said Fauci. “I think he is wrong about this.”
By going with just one dose, “you are at a very weak level. Good enough to provide protection, but if you quintuple it, you fall outside of the protection card. “
The mRNA vaccines were approved for use in the US based on data from clinical studies showing that two doses of the vaccines taken a few weeks apart are approximately 95% effective in preventing symptomatic infection. Clinical studies for both vaccines show that the second dose provides a large boost to protective antibodies.
CDC guidelines continue to recommend two doses of the Pfizer and Moderna vaccines, and experts at the CDC’s Advisory Committee on Immunization Practices (ACIP) meeting on Monday said there is not enough scientific evidence to support a vaccination strategy that would second dose would slow down or eliminate everything together.
“Five studies have shown that delaying the second mRNA dose may make some people less protected against the SARS-Cov-2 variants,” said Dr. Heather Scobie of the CDC at the ACIP meeting.
Fauci told The Washington Post this week that there are “risks on both sides” of switching to a single dose or sticking with the two. Experts fear that a single-dose strategy could lead to more coronavirus variants and more doubt and confusion during an already complicated vaccine rollout.
‘We tell people [two shots] is what to do … and then we say, ‘Oops, we changed our mind’? Fauci said. “I think that would be challenging in terms of messaging to say the least.”
That does not mean that more dosage changes will not follow.
Researchers around the world are investigating the efficacy of single doses of mRNA vaccines. Meanwhile, the J&J vaccine – currently approved as a single dose vaccine – is also being tested as two doses to see if it will provide more protection.
Study single doses
Some countries are already implementing single-dose strategies to expand their offerings and provide some protection for more people.
As of late December, the UK has stopped telling people to skip the second injection, but has delayed the second dose of the Pfizer / BioNTech vaccine to prioritize the first doses. The delay allowed the interval between doses to be extended to 12 weeks instead of about three.
In response to the change in vaccination schedule, Pfizer said at the time that it has not tested its vaccine in this way.
“The Phase 3 study by Pfizer and BioNTech for the Covid-19 vaccine was designed to evaluate the safety and efficacy of the vaccine on a 2-dose schedule separated by 21 days,” Pfizer said. “There are no data to demonstrate that protection is maintained beyond 21 days after the first dose.”
There is some research to suggest that the Pfizer / BioNTech vaccine offers some protection after a single dose.
Investigators at Israel’s largest hospital looked at what happened after 7,000 staff were vaccinated with the first dose of the Pfizer / BioNTech vaccine. In the second to fourth week after they received the first injection, the rate of symptomatic infections decreased by 85%.
However, it is still unclear how long this protection would last. The study also noted that the people vaccinated were “younger and healthier” and may not reflect the wider population.
There is also some research to suggest that one dose may be sufficient for people with a previous infection. Two articles published last week in The Lancet found that just one dose of the Pfizer / BioNTech coronavirus vaccine can elicit a strong enough immune response in people who have already had the coronavirus that it could protect against future infections. France has already recommended that people who were previously infected only get one dose.
And in a letter sent to the New England Journal of Medicine in February, Canadian researchers went through the documents Pfizer / BioNTech submitted last year for emergency use authorization and concluded that a single dose is still at least 90% effective .
“With such a very protective first dose, the benefits of a scarce vaccine supply could be maximized by delaying second doses until all members of the priority group are offered at least one dose,” they added.
But they noted that it is still unclear how long the protection lasts with just one dose.
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