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Scientists at the National Institutes of Health and the drugmaker Moderna are analyzing vaccine research data to see if they can double the supply of the company’s coronavirus vaccine by cutting doses in half, a move that would help alleviate vaccine shortages as the country surpassed more than 21 million virus cases.
The research, which also involves scientists from Operation Warp Speed, the government’s vaccine initiative, could take about two months, Dr. John Mascola, the director of the Vaccine Research Center at the N.I.H., said in an interview Tuesday.
The data analysis, which Dr. Mascola said has been long planned as part of the vaccine research effort, comes amid a broader scramble to increase vaccine supply. Late last month, the Trump administration sealed a deal with Pfizer to increase that company’s vaccine supply by 100 million doses.
“It’s important to do these analyses that we’re doing, and have all that data in our pocket in the event that there’s a need to use it,” Dr. Mascola said.
The vaccine rollout has been troubled from the start. For the moment, the problem is not a shortage of vaccine, but rather that state and local governments are having trouble distributing the vaccine doses they already have.
The prospect of doubling the supply of Moderna doses was first raised on Sunday by Dr. Moncef Slaoui, the head of Operation Warp Speed, who said on the CBS program “Face the Nation” that data from Moderna’s clinical trials demonstrated that people between the ages of 18 and 55 who received two 50-microgram doses showed an “identical immune response” to the two 100-microgram doses.
That is true, said both Dr. Mascola and Dr. Anthony S. Fauci, the director of the National Institute for Allergy and Infectious Diseases, which includes the vaccine research center. But Dr. Slaoui also went one step farther, and said federal officials and Moderna were discussing possibly halving each of Moderna’s two doses — a remark that prompted pushback from the Food and Drug Administration, which would have to approve any change in the dosing regimen.
In a statement posted on its website Monday night, the F.D.A. said a proposal for half-doses of the Moderna vaccine was “premature and not rooted solidly in the available science.” The finding Dr. Slaoui cited came from an early Phase II clinical trial, which involved hundreds of people and was designed to test only for immune response, and not for the effectiveness of the vaccine, Dr. Fauci said. It compared the immune response in people given 50 micrograms against those given 100 micrograms.
The larger Phase III trial that found the vaccine effective involved 30,000 people, half of whom were given the 100-microgram dose and half of whom were given placebo.
In order to provide the F.D.A. with the kind of data it would need to approve a change in dosing, scientists must first study blood samples from patients who participated in the Phase III trial to determine precisely what immune response correlates with protection against Covid-19.
Then, Dr. Mascola said, researchers would have to either look back at patients from the Phase II trial, or conduct a new one, to demonstrate that patients who received the 50 milligram dose developed the threshold immune response. If the results looked promising, he said, “all this then needs to be put together as a data package for review and discussion with F.D.A.”
On Tuesday, Dr. Jerome Adams, the U.S. surgeon general, urged states not to stick rigidly to the Centers for Disease Control and Prevention guidelines about whom to vaccinate first. He said states should “move quickly to other priority groups” if fewer health care workers agree to be vaccinated.
Asked about Dr. Adams’s remarks, a C.D.C. spokeswoman said the agency had made clear in written guidance that states did not need to vaccinate everyone in a priority group before moving on to the next group.