FDA Says Two Doses of Coronavirus Vaccines Needed

FDA: 2 doses of the 1:21 vaccine are necessary

(CNN) -

Anyone receiving the Moderna or Pfizer vaccine should receive two full doses, two senior officials from the U.S. Food and Drug Administration (FDA) said Monday.

They also ruled out other ideas to expand the vaccine supply, saying that people who speculate on the possibility of getting by with just one dose or cutting it in half are misinterpreting the data.

"We have been following discussions and news reports on how to reduce the number of doses, extend the time between doses, change the dose (half dose) or mix and match vaccines to immunize more people against covid-19," they said in a statement FDA Commissioner Dr. Stephen Hahn and Dr. Peter Marks, who head the FDA's vaccine division.

'These are all reasonable questions to consider and evaluate in clinical trials.

However, at this time, it is premature to suggest changes to FDA-authorized doses or schedules for these vaccines and is not strongly based on the available evidence.

Without adequate data to support such changes in vaccine administration, we run a significant risk of putting public health at risk, undermining historic vaccination efforts to protect the population from COVID-19, "they added.

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Operation Warp Speed's chief adviser, Moncef Slaoui, told CNN on Sunday that the FDA would consider giving half doses of Moderna's covid-19 vaccine to people ages 18 to 55, which could make the vaccine available for twice as many people in this age group.

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Slaoui said previous data shows that the vaccine appeared to elicit effective antibody responses among volunteers under the age of 55 who received the full 100-microgram dose or half the dose.

While an FDA briefing document last month also refers to these "comparable" immune responses from Moderna's phase 2 study, the full data has yet to be released.

The doses of the vaccines against the covid-19 in the USA

But Marks and Hahn said these findings covered only a very few people who weren't followed for a long time to see if their immune responses held up over time.

“What we have seen is that data in company presentations regarding the first dose is commonly misinterpreted.

In the phase 3 trials, 98% of the participants in the Pfizer-BioNTech trial and 92% of the participants in the Moderna trial received two doses of the vaccine at an interval of three or four weeks, respectively, ”they wrote.

'Participants who did not receive two doses of the vaccine within three to four weeks were generally only followed for a short period of time, so we cannot conclude anything definitive about the depth or duration of protection after a single dose of the vaccine based on the single dose percentages reported by the companies ”.

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Two doses of covid-19 vaccines are needed

British officials have said they will allow more than 21 days between doses of Pfizer vaccines and would consider allowing people to get vaccinated with two different vaccines.

Hahn and Marks rejected these ideas for the United States.

“Available data continues to support the use of two specific doses of each licensed vaccine at specific intervals.

For the Pfizer / BioNTech vaccine against covid-19, the interval is 21 days between the first and second doses.

And for Moderna's vaccine against covid-19, the interval is 28 days between the first and second doses, "they wrote.

It's understandable that people want to stretch the vaccine supply, they said.

But it is not advisable.

"If people don't really know how protective a vaccine is, there is the potential for harm because they can assume they are fully protected when they are not and consequently alter their behavior to take unnecessary risks," they said.

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“Today the first vaccines in the UK against covid-19 begin.

Thank you to our NHS, to all the scientists who worked so hard to develop this vaccine, to all the volunteers, and to all those who have followed the rules to protect others.

We will get through it together, "UK Prime Minister Boris Johnson tweeted. (Photo: JACOB KING / POOL / AFP via Getty Images)

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At 6:31 am, Margaret Keenan, known to her friends and family as Maggie, received the first dose from Nurse May Parsons at Coventry University Hospital.

(Photo: JACOB KING / POOL / AFP via Getty Images)

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Maggie, who will turn 91 next week, is a former jewelry assistant who retired just four years ago.

He has a daughter, a son and four grandchildren and hopes to be able to go out again once he receives the second dose of the vaccine.

(Photo: JACOB KING / POOL / AFP via Getty Images)

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Margaret said: “I feel so privileged to be the first person to be vaccinated against covid-19, it is the best anticipated birthday gift I could wish for because it means that I can finally look forward to spending time with my family and friends in the new year, after being alone most of the year. "(Photo: JACOB KING / POOL / AFP via Getty Images)

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"I can't thank May and the NHS staff enough who have taken such tremendous care of me, and my advice to anyone who is offered the vaccine is to take it; if I can have it at 90, you can too!" .

(Photo: JACOB KING / POOL / AFP via Getty Images)

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A nurse administers the vaccine to patient William "Bill" Shakespeare, 81.

(Photo: JACOB KING / POOL / AFP via Getty Images)

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UK Health Secretary Matt Hancock said on Sky News: "I am very excited to see those photos. It has been such a difficult year for so many people and we have finally gotten over it, our light at the end of the tunnel, as many people say. And just seeing Margaret there, it seems so simple to have an injection in the arm, but that will protect Margaret and protect the people around her. "

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Michael Tibbs, 99, received the Pfizer vaccine from Liz Rix, a senior nurse at Queen Alexandra Hospital in Portsmouth.

(Photo: Ewan Galvin - Pool / Getty Images)

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"If we can do that for everyone who is vulnerable to this disease, then we can move on and we can get back to normal," said Health Minister Hancock.

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Boris Johnson toured a recently opened vaccine center in London early Tuesday.

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The staged vaccination program will serve patients 80 years of age and older who already attend the hospital as outpatients, and those who are being discharged after a hospital stay, among the first to receive the life-saving dose.

(Photo: DOMINIC LIPINSKI / POOL / AFP via Getty Images)

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Retired nurse Suzanne Medows administers the Pfizer vaccine to Ranju Shukla at the Royal Victoria Infirmary in Newcastle, northern England.

(Photo: OWEN HUMPHREYS / POOL / AFP via Getty Images)

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Waiting room to receive the Pfizer / BioNTech vaccine in Cardiff, Wales.

(Photo: JUSTIN TALLIS / POOL / AFP via Getty Images)

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UK Covid-19 Vaccine Information Booklet.

(Photo: OWEN HUMPHREYS / POOL / AFP via Getty Images)

Dr. Paul Offit, an infectious disease specialist at the University of Pennsylvania, told CNN that he thought cutting vaccine doses in half was a bad idea.

'There are no data on the efficacy of half the dose.

If you use half the dose, you are simply making something up.

You just hope you're right, ”added Offit, a member of the Vaccines and Related Biologics Advisory Committee.

"Why would you dare to invent something when you don't know if it works or not?"

Dr. Arnold Monto, who was acting chairman of the committee during last month's meetings to consider the vaccine applications of Moderna and Pfizer, told CNN on Monday that reducing the dose would be out of the question.

"This would be a very unusual step, since it was not studied in Phase 3, but emergency use is also a very unusual step," said Monto, a professor of epidemiology at the University of Michigan.

- CNN's Dr. Sanjay Gupta and Elizabeth Cohen contributed to this story

Coronavirus Vaccine