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COVID-19 vaccine starts working within two weeks after first shot

COVID-19 vaccine starts working within two weeks after first shot


There are no serious safety concerns with the Pfizer and BioNTech shot

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NHS England Starts Covid-19 Vaccination Campaign
Staff administer the Pfizer and BioNTech to people in the UK.
Photo by Victoria Jones / Pool / Getty Images

The Pfizer and BioNTech COVID-19 vaccine is safe, effective, and starts working within about two weeks of the first dose, according to documents published by the Food and Drug Administration today.

The materials are the first look at the vaccine data from the perspective of the FDA staff, rather than the drug companies. They were released ahead of the agency’s vaccine advisory committee meeting on December 10th. Like data released by Pfizer, the FDA’s briefing document shows that the vaccine is 95 percent effective at protecting against symptomatic COVID-19, and there are no serious safety concerns with the shot. It worked similarly for people in all racial and ethnic groups and of all ages in which it was tested. (There isn’t data available on children younger than 16.)

“This is what an A+ report card looks like for a vaccine,” Akiko Iwasaki, an immunologist at Yale University, told The New York Times.

While the FDA will decide whether to authorize the vaccine on Thursday, other countries have already started administering the shots. Early this morning, a 90-year-old woman in the United Kingdom became the first person to receive the Pfizer and BioNTech vaccine outside of a clinical trial. The UK authorized the vaccine for emergency use last week and started a mass vaccination campaign today.

Protection could kick in quickly. About 10 days after the first dose, more cases of COVID-19 started appearing in the group of people who received the placebo than in the group that took the vaccine, according to the materials.

That doesn’t mean one shot is enough, however. The study wasn’t designed to figure that out, and most participants went on to get a second dose. The second dose of a vaccine functions as a booster, triggering the immune system to produce long-lasting memory cells that stick around to protect against the virus in the future. Even if the first dose offers some protection in the short-term, the second dose is critical.

The FDA’s analysis notes there are still data gaps around the vaccine. The clinical trial only followed people for two months, and it’s unclear how long protection from COVID-19 will last. It’s unclear how well the vaccine could work in kids, and there isn’t data on pregnant people.

The trial also wasn’t designed to check if the vaccine can stop people from spreading the virus. Preventing symptomatic illness is a huge benefit. It would prevent some of the devastating consequences of the virus, keep people out of the hospital, and ease the strain on the health care system. But if people who were vaccinated could still have asymptomatic infections, the vaccines wouldn’t necessarily stop the spread entirely. Other measures, like mask wearing and social distancing, would still be important.

The FDA’s vaccine advisory committee will meet on Thursday, and the agency could authorize the Pfizer and BioNTech vaccine for emergency use soon after. States are preparing to give the first shots to health care workers on December 15th. The company said it could have enough of this vaccine for 12.5 million people by the end of 2020, and the United States has access to 100 million more doses — enough for 50 million people with two shots each. The Trump administration turned down an option to order more doses from Pfizer, raising concerns about shortages through the spring if there are not vaccines from other companies available.

You can read the FDA’s full report here.