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