The Covid-19 vaccine developed by British drugmaker AstraZeneca Plc and Oxford University will likely be authorized for emergency use in the United States in April, the chief adviser for the US Covid-19 vaccine program said on Wednesday.
Operation Warp Speed chief adviser Dr Moncef Slaoui said recruitment for the British drugmaker's late-stage US trial is almost complete with over 29,000 participants enrolled.
"We project if everything goes well with readout and emergency use authorization may be granted somewhere in April," Slaoui said.
British regulators approved AstraZeneca's vaccine Wednesday, the first country in the world to do so, based in part on unpublished data.
Several scientists have raised doubts about the robustness of results from its British and Brazilian trials, showing the shot was 90% effective in a sub-group of trial participants. That group, by error initially, received a half dose followed by a full dose. But the efficacy was 62% if the full dose was given twice, as it was for most participants.
Slaoui said it would ultimately be up to the US Food and Drug Administration as to how to evaluate the vaccine for US authorization.
Slaoui was also cautious about whether the United States should implement similar guidance as the UK regulators to space out the second dose of Pfizer Inc's by as much as 12 weeks, longer than what was studied in clinical trials.
While early data suggests that people have some protection against the virus after receiving their first dose, the length of time that protection lasts has not been studied, Slaoui said.
Officials said that 14 million doses of Pfizer's and Moderna's have been distributed to states, short of their goal to send enough doses to vaccinate 20 million Americans this month.
Only about 2 million Americans have been vaccinated thus far and officials said they were still studying why immunizations were slower than they anticipated.