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The FDA’s Expert Panel Just Greenlit The First COVID-19 Vaccine In The US. Here Are 5 Things To Know About It.


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A nurse from the Belfast Trust Vaccine Team prepares to inject care home staff with the Pfizer/BioNtech COVID-19 vaccine.

An expert FDA panel voted Thursday to recommend Pfizer’s COVID-19 vaccine, bringing the US much closer to nationwide distribution of shots needed to control a pandemic that’s killing 3,000 people a day.

In a 17 to 4 vote, with one abstention, the independent panel of medical safety experts found the vaccine’s two shots, which are likely 95% effective in preventing the disease, had benefits that outweighed their risks for people 16 and older.

“The FDA has been laboring long and hard,” said panel chair Arnold Monto of the University of Michigan School of Public Health.

The final decision now heads to FDA chief Stephen Hahn, who is expected to soon issue an emergency use authorization for the vaccine. Health officials have promised that they will ship out an initial 2.9 million doses nationwide within 24 hours of Hahn’s decision.

On Wednesday, the United Kingdom began administering shots of the vaccine and Canada became the second country to approve Pfizer’s shots. The vaccine requires two doses, spaced 21 days apart.

At the panel meeting, FDA scientists and Pfizer representatives presented efficacy and safety data from a large clinical trial of the vaccine ahead of the vote. Here’s what you need to know from the numbers and the questions the experts asked:

1. The vaccine offers very good protection against COVID-19.

Infections rising in unvaccinated people (red) against vaccinated people (blue) after one dose.

FDA scientists confirmed Pfizer’s analysis of preliminary data from its trial of 44,000 people, which found that the vaccine had an efficacy rate of 95% among study participants when compared with people who got placebo shots. The vaccine’s protection began one week after participants received their second shot. The results found the vaccine equally efficacious among all age groups, genders, and races, particularly welcome news in a pandemic that has struck the elderly and minorities hard.

This rate of protection is extremely high — and caught many scientists by surprise. The FDA requires that any COVID-19 vaccine that is submitted for emergency authorization shows at least 50% efficacy, while the flu shot is typically about 60% effective.

It’s important to remember that vaccine “efficacy” is simply the statistical drop in COVID-19 being diagnosed in the vaccinated half of the people in a study, compared to the half of participants that got a placebo shot. It doesn’t tell you what the chances are that you will be protected by the vaccine in the real world.

The level of protection was calculated from 162 people who got COVID-19 in the placebo arm of the trial versus 8 people who got the vaccine and still got infected. Only a handful of severe cases were reported, making it hard to definitively conclude that the vaccine can help prevent the worst outcomes of COVID-19.

It will be important for everyone receiving their first shot to make sure to return after 21 days for their second. A first shot on its own was only about 52.4% efficacious in lowering the rate of COVID-19 diagnoses. Operation Warp Speed chief scientist Moncef Slaoui, speaking Wednesday, said that was not good enough to justify making the Pfizer vaccine a single-dose shot, but since a flattening of COVID-19 diagnoses became apparent about 12 days after even just one shot in the study population, that suggests the vaccine will be very effective once it starts rolling out in the wider population.

“Hopefully we will start impacting people’s lives very quickly after the onset of the campaign to immunize,” Slaoui said.


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Healthcare worker Demetra Ransom comforts a patient in the COVID-19 ward at United Memorial Medical Center in Houston on Dec. 4.

2. The shots come with side effects.

Mild side effects such as arm soreness, fatigue, fevers, chills, and headaches were significantly more common for people who got the COVID-19 vaccine than in some other common vaccines such as the flu shot. About a quarter of the participants reported some kind of reaction, primarily arm soreness, followed by fevers, chills, tiredness, and headaches. Only about 1% reported nausea or an upset stomach.

That rate of reactions is similar to the very effective shingles vaccine, noted Slaoui. “There is no free lunch,” he said. “If you have a very good immune response you notice it. But it’s not the safety issue, it’s actually an immunogenicity marker,” where a powerful vaccine kicks up a stronger reaction to a shot than a weaker one.

“I had adverse effects, and I would still tell people go get a shot,” said UCLA nursing professor Kristen Choi, who participated in the Pfizer clinical trial and had a high fever, nausea, and dizziness the day after her second injection. “You might plan to take the day off after getting the shot.”

The rate of serious side effects — swollen lymph nodes, heart arrhythmias, and one shoulder injury — was about 1 in 200 in both the vaccine recipients and in the placebo group.

The FDA is requiring all drug companies submitting COVID-19 vaccines for emergency authorization to provide two months of safety data for at least half of their trial participants. The health agency and the CDC will continue safety monitoring using several surveillance systems that will keep track of vaccine recipients who develop any side effects.

One set of reactions worth monitoring are cases of Bell’s palsy, a temporary weakening of the muscles on one side of the face, reported in four people who received the vaccine. To determine whether the illnesses were linked to the vaccine, safety monitors look for incidents of these reactions above the background numbers seen in the general population. UK regulators assessed the incidents as not statistically unusual, since the trial included tens of thousands of people. But the FDA is recommending that healthcare providers monitor for further cases as the vaccine is distributed widely.

3. People who have severe allergic reactions should probably avoid this vaccine.

On Wednesday news came from the UK’s rollout of the Pfizer vaccine of strong allergic reactions in two health workers who received their first shots. Both individuals had a history of allergic reactions strong enough that they carried EpiPens with them meant to stave off such events, and both recovered from the reactions.

Following the reports, the UK’s health regulator announced that people with a “significant history of allergic reactions” should not be given the vaccine. On Thursday, an FDA official noted that the vaccine’s prescribing information had already been adjusted to warn that it should not be given to people with a known history of severe allergic reactions to any component of the vaccine.

People with a history of allergic reactions were excluded from Pfizer’s trial. It’s normal for some safety issues like this to become clear as a vaccine is distributed to millions of people outside of the confines of a clinical trial. Pfizer executive Bill Gruber said that in the course of the trial, there hadn’t been any indication that the vaccine caused severe allergic reactions.

But Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia, said that Pfizer should go one step further in efforts to be clear with the public and conduct studies of the vaccine specifically in people with allergies to eggs or peanuts.

While he made it clear that he didn’t think this was a reason to hold up the vaccine, he expressed concern that millions of people with allergies will not get vaccinated without more reassurance. “I think we just need to offer people some solace this is not going to be a problem,” Offit said. “This is going to be an issue and we need to have some data to arm ourselves with.”

Vaccine centers however are well prepared to handle allergic reactions when they occur, University of California San Francisco vaccine developer Joel Ernst noted. “I think the implications for anyone without a history of severe allergies (and I take that to mean, reactions that needed emergency treatment), are negligible,” he said, by email.


Saul Loeb / Getty Images

An employee makes dry ice pellets at Capitol Carbonic, a dry ice factory, in Baltimore, Maryland, on Nov. 20. Pfizer’s vaccine needs to be transported and stored at -94 degrees Fahrenheit.

4. There are still safety unknowns for some groups, including pregnant people.

Along with those people with histories of serious allergic reactions, there are other groups of people for whom safety data is lacking, notably pregnant people.

That matters, because the first priority group for the vaccines are the nation’s 21 million health care workers, and three quarters of them are women. Perhaps 300,000 of them might become pregnant or be nursing in the next year, according to estimates presented at an HHS advisory committee meeting last Friday. Although pregnant women were excluded from entering Pfizer’s clinical trial, 23 women did become pregnant while enrolled, a dozen of them in the vaccine group, too small of a number for any safety statistics. The AstraZeneca vaccine is including some pregnant women in its trial, but those results are not expected to be delivered to FDA until January.

The study added 100 teens aged 12 to 15, but that was too few vaccine-takers to generate an estimate of vaccine efficacy for the age group and side effect data about them was left out of Pfizer’s authorization application. Side effect data for 16 and 17 year olds in the trial did not look different than adults though, suggesting that for older children, at least, the vaccines look safe.

On Thursday, several members of the FDA advisory committee expressed concern about whether there was enough data from people in that age group to clear the vaccine for their use. (The trial included 153 16- and 17-year-olds.)

5. Healthcare workers and nursing homes are first in line for the vaccine.

Although Operation Warp Speed promises to start shopping doses within 24 hours of the FDA issuing an emergency authorization for their distribution, where they end up will depend on each state’s plans. The CDC recommends the first doses go to healthcare workers, and to residents and staff at nursing homes, but governors will have the final say, according to HHS head Alex Azar.

While some states are following the CDC recommendations, others like Texas and Florida are also prioritizing people 65 years of age and older as well as ”vulnerable, frontline workers.” A patchwork pattern of vaccine distribution might result nationwide, with neighboring states first getting vaccines to different groups. .

At least 36 states are working with CDC and pharmacy chains to distribute vaccines in long term care facilities with the first shipments, according to OWS shipping chief Army Gen. Gustave Perna.

Unless you are in a high priority group, or a clinical trial, it may take months for other Americans to get vaccinated. The plans unveiled on Wednesday were for 20 million people to get the first shot before the end of the year, 30 million in January, and 50 million in February. The nation’s population is almost 330 million people, and the hope now is that everyone who wants a shot can get one by the end of June.


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