Americans likely won’t receive AstraZeneca’s coronavirus vaccine before April because of lingering questions about its effectiveness in certain groups, a top Trump administration health official said hours after U.K. regulators authorized the company’s shot Wednesday.
The prediction by Moncef Slaoui, head of Operation Warp Speed, moves back the U.S. government’s timeline for greenlighting the AstraZeneca shot by at last two months. Slaoui earlier this month estimated the British drugmaker would file for emergency use authorization with the Food and Drug Administration as early as February.
“We project, if everything goes well, that the readout and emergency use authorization may be granted somewhere early in the month of April,” Slaoui said on a press call Wednesday.
Questions about the vaccine: The U.S. has ordered 300 million doses of the two-shot vaccine candidate, which has faced questions during development. A late-stage trial was paused this fall to assess a serious reaction to a shot, while promising results from an early readout on the shot were attributed to a dosing mistake.
Slaoui said that while the AstraZeneca vaccine appears very effective against severe disease, its efficacy among elderly people is “effectively unknown” because few older people were enrolled early in the trial. He said that remains his biggest question about the company’s shot, given the virus’ impact on elderly people.
British regulators on Wednesday morning became the first in the world to authorize the AstraZeneca vaccine for use. Rather than hold back doses to ensure people quickly get a second shot, British health officials said they would broadly vaccinate the country with the first doses and provide the second within three months. They said the move would provide some level of protection to the whole country amid climbing infections and a new variant of the virus that appears to be more transmissible.
But the effectiveness of the AstraZeneca vaccine is still unclear, particularly when doses are spaced out. AstraZeneca’s vaccine so far shows 62 percent efficacy when used as two full doses administered 28 days apart. But after a dilution mistake in one arm of a phase 3 trial, scientists found that the vaccine was 90 percent effective when a small group received a half-dose first.
U.S. regulators need more evidence: The drugmaker has said that the combined results showed 70 percent efficacy, but Slaoui suggested that U.S. regulators would not be satisfied by that conclusion.
“As far as the American people are concerned, I think it’s important to say one vaccine has 95 percent efficacy, another vaccine has X percent, whatever that number,” Slaoui told reporters, referring to the high efficacy rates for the Pfizer and BioNTech and Moderna vaccines that the FDA has authorized. “We need a clear and concrete number more than a number that is accumulated by adding together different trials with different schedules and different materials.”
Slaoui also questioned Britain’s dosing strategy. He said it’s possible a booster shot can be more effective when administered months later, but he said that the U.K. decision was based on theory rather evidence.
“It’s important, I think, to use the vaccine based on how you studied it,” he said.
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