Only after the agency has given the green light will a first, limited group of high-risk people be able to access the shots. Government officials anticipate having enough vaccine to inoculate about 20 million people with the two-dose regimen in the U.S. in December, between Pfizer’s vaccine and a second shot likely to be considered for emergency authorization soon, from biotechnology company Moderna. The United States will receive about half of the 50 million doses Pfizer is aiming to produce by the end of the year.
There will probably be enough vaccine for 25 million to 30 million people a month in early 2021, according to Moncef Slaoui, chief scientific adviser of Operation Warp Speed, the federal government initiative to speed up vaccine development. He did not specify how many doses each company would contribute.
Glimpses of the Pfizer data through news releases have so far exceeded expectations: The two-dose vaccine regimen was 95 percent effective at preventing disease in clinical trials and had no major safety problems, according to the company. It was 94 percent effective in people over 65, a group of critical concern because older people are more likely to develop life-threatening illness after contracting the virus. The companies are also submitting two months of follow-up data on 38,000 people, far more than the minimum of half the participants in their 44,000-person trial. They will also present safety data on 100 children between 12 and 15 years old, a group they only recently began to include in their trial.
Once Pfizer and BioNTech file their application, those findings will be scrutinized by regulators — including at a full-day advisory committee meeting in which external scientists will meet to make recommendations to the agency on whether it should clear the vaccine for broader use.
“My message to the American people is to hang in there with us. Take the simple steps that the doctors have talked about today because there is a light at the end of the tunnel. This isn’t forever,” Health and Human Services Secretary Alex Azar said in a briefing Thursday.
Pfizer’s announcement that it will file for emergency authorization follows two weeks of blockbuster vaccine news, a period during which more than 1.5 million people in the United States were diagnosed with covid-19, the illness caused by the coronavirus.
On Wednesday, Pfizer announced its 44,000-person vaccine trial had hit the necessary endpoints for safety and efficacy and that it could file for emergency authorization within days. The vaccine was 95 percent effective at preventing disease in the large clinical trial, and Pfizer and BioNTech had gathered sufficient safety data to support an application, with no major safety problems identified.
On Monday, a vaccine candidate from biotechnology firm Moderna clocked in with nearly 95 percent efficacy at an early analysis.
Half of the participants in Pfizer’s trial received two doses of the study vaccine and half received two shots of saline. Then, the investigators waited to see which participants fell ill as they were exposed to the virus in their normal lives.
Out of 170 cases of covid-19 so far, 162 were in the placebo group — a strong signal the vaccine protected people. Nine in 10 cases of severe illness were in the placebo group, another strong sign the vaccine protected against mild and serious cases. The most common adverse event rated as “severe” in the trial was fatigue, in 3.7 percent of participants after the second dose.
An emergency authorization for a vaccine is typically a lower standard than full approval. Still, FDA guidelines sought to set a high standard for a vaccine, even under emergency authorization . That guidance required a vaccine be at least 50 percent effective, with a minimum of two months of safety data on half the participants.