FDA review confirms safety and efficacy of Pfizer coronavirus vaccine

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WASHINGTON – A two-shot coronavirus vaccine developed by Pfizer and German firm BioNTech appears to be on the cusp of regulatory clearance, after a 53-page review published Tuesday confirmed that the vaccine appears to meet the standard for emergency use authorization.

The Food and Drug Administration briefing document is the first hint of U.S. regulators’ assessment of the vaccine as the agency’s career scientists approach one of the most momentous decisions in the FDA’s history. It is also the most detailed independent review yet of data that has so far been known only through company news releases.

The FDA’s career scientists undertook their own thorough analysis of the data over the last two weeks and confirmed Pfizer’s assessment that the vaccine regimen was 95% effective at preventing disease in large clinical trial and had tolerable short-term side effects, including sore arms, fatigue, headaches, muscle pain and chills that typically resolved within one to two days. The review also found evidence that the vaccine, which is given in two doses, three weeks apart, began to protect people after the first dose.

The document spells out that the vaccine has cleared the minimum threshold of being at least 50% effective and states that the two months of follow-up on 38,000 participants in the trial provide evidence of “a favorable safety profile, with no specific safety concerns identified that would preclude issuance of an [emergency authorization].”

On Thursday, a group of advisers to the FDA will meet for a full-day public meeting to discuss the data and make recommendations on whether the vaccine merits authorization for immediate use. A decision, informed but not dictated by that debate, is expected to come within days of the meeting. The first doses are expected to be shipped within hours, with a target of 6.4 million doses distributed in the first week.

British regulators cleared the vaccine for use last week and administered the first shots Tuesday to elderly people and nursing home workers, but their review relies more heavily on the company’s data analysis.

The vaccine was tested in about 44,000 people, half of whom received two doses of the real vaccine three weeks apart, and half of whom received shots of saline. People then went about their normal lives and were exposed to the virus in their communities. There were 170 cases of covid-19, the disease caused by the virus, in the study. Only eight of those cases were in the group that received the vaccine, an overwhelming signal of efficacy and well above the minimum threshold the agency laid out this summer.

One of the biggest questions about the coronavirus vaccines is whether they work equally well in all people, particularly those at highest risk of severe illness, including older people, those with underlying medical conditions and minority groups. The vaccine trials sought to recruit diverse populations. The FDA review found that efficacy was similar “across age groups, genders, racial and ethnic groups, and participants with medical comorbidities associated with high risk of severe COVID-19.”

Another major question about the vaccines has been whether they can prevent both mild and the most devastating, severe cases of disease. There were 10 cases of severe illness in the trial, with nine of those in the placebo group.

The Pfizer vaccine is the first of two vaccines to be considered by regulators this month based on a novel technology that uses snippets of genetic material to teach the body’s own cells to build the spiky protein that coronaviruses use to latch onto cells. The immune system, exposed to the spike, can then learn to recognize and block the real virus.

One point of debate among outside advisers to the agency this week could be the length of follow-up on a vaccine technology that has never been used in an approved product. The FDA is asking its committee to vote on whether the vaccine has been demonstrated to be effective in preventing covid-19 in people ages 16 and older.

Pfizer has projected that the United States will receive about half of its global supply through the end of the year – about 25 million doses. Government officials expect about another 20 million doses to be provided by Moderna, which is about a week behind the Pfizer and BioNTech vaccine. Pfizer will deliver the balance of the 100 million doses the United States has purchased in the first few months of next year, enough for 50 million people.

The United States approached Pfizer to buy another 100 million doses this past weekend, but was informed the supply may not be available until late June, The Washington Post reported. That raises questions about whether the U.S. goal to create enough vaccine for the entire population by the summer could slip.