The Food and Drug Administration released a 50-page report on Pfizer’s COVID-19 vaccine Tuesday — a telling preview of the agency’s views on a vaccine it could authorize in days.
We reached out to two San Diego scientists intimately familiar with vaccine research to understand the report’s findings and their significance: Erica Ollmann Saphire of La Jolla Immunology and Dennis Burton of Scripps Research.
The report leaves a few lingering questions, and no vaccine will be an instant fix for a virus that has claimed the lives of 285,000 Americans. But the bottom line?
“It bodes well, and it’s reassuring,” Saphire said. “I think the light at the end of the tunnel is getting pretty close.”
The FDA’s report briefs members of the agency’s vaccine advisory committee, who will meet Thursday to decide whether to recommend an emergency use authorization for Pfizer’s vaccine. That recommendation carries considerable weight because while the FDA technically doesn’t have to heed the advice of its advisory committee, it generally does.
The report contains a lot of information. Pfizer conducted a massive clinical trial of about 44,000 participants, and there are plenty of ways to slice and dice that data. By comparison, Shingrix, a shingles vaccine for older adults, received FDA approval after a trial of 30,000.
“They’re not skimping on the quantity of data,” Saphire said.
Pfizer and other vaccine developers are aiming for a lower bar than full approval: emergency use authorization (EUA), which allows for rapid rollout during a public health emergency. The FDA has said it will authorize a COVID-19 vaccine if it’s at least 50% effective, if its benefits outweigh any risks, and if at least half of trial participants have been monitored for two months or longer.
On Nov. 18, Pfizer sailed over the FDA’s 50% cutoff by announcing that its vaccine was 95% effective after 162 volunteers given the placebo got COVID-19 compared to 8 people who received the actual vaccine.
The FDA broke down vaccine effectiveness by participant age, gender, race, ethnicity and medical history. Vaccines generally don’t work as well in older adults, and 80% of COVID-19 deaths have been among people 65 and up. Common preexisting conditions such as obesity, high blood pressure and diabetes have also consistently made people more likely to develop severe disease.
“It looks pretty effective across all the groups that I could see,” said Burton, whose lab has teamed with others to study how the immune system responds to the coronavirus.
That suggests that the vaccine works well for a wide swath of the population, including those hit hardest by the coronavirus. Also notable: hints that even a single dose of the vaccine provides some protection against the disease.
Pfizer’s vaccine is given as two shots, three weeks apart. During that three-week window, those who received the vaccine were about half as likely to develop COVID-19 as those given the placebo. That makes sense, says Saphire, given that the first injection sparks an immune response that the second shot boosts.
That’s good news for the 28,000 San Diegans who will get Pfizer’s initial COVID-19 vaccine doses, which could arrive in mid-December. The county will use all of its supply to vaccinate each person once, counting on a future shipment arriving in time for the booster shot.
The FDA report suggests that those people — likely a mix of health care workers and nursing home residents — could have some protection against COVID-19 while they wait for the second shot, though the agency was careful to say it can’t clearly conclude that a single dose is protective.
San Diegans who have participated in Pfizer’s vaccine trial reported feeling flu-like symptoms for a couple of days after their injection. That’s consistent with the recent report’s finding that the most common side effects were pain or itchiness around the injection site, fatigue, a headache and muscle soreness.
These side effects were mostly brief and mild, and the FDA found “no specific safety concerns identified that would preclude issuance of an EUA.”
If the FDA’s vaccine advisory committee recommends on Thursday that the agency authorize Pfizer’s vaccine, the FDA could do so within days. U.S. government officials have indicated that the first 6.4 million doses of vaccine would be distributed within 24 hours of emergency authorization.
That’s great news, says Burton, but he cautions there’s still a lot we don’t know about this vaccine — like how well it prevents COVID-19 in children, how long protection lasts and how well it prevents you from spreading the coronavirus. In other words, you’ll want to hold onto that mask after getting your vaccine.
“Even if you’re protected having got the vaccine, you could still get a very low level of infection and then pass it on to somebody else,” Burton said. “Definitely, masks should still be required.”
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