COVID-19 Vaccine FAQ: Safety, Side Effects, Efficacy
Dec. 17, 2020 — Pfizer began shipping the first batch of COVID-19 vaccines to all 50 states this week, capping months of anticipation, development, clinical trials, and regulatory reviews.
Amid efforts to fast-track the Pfizer/BioNTech vaccine, the FDA granted emergency use authorization for the vaccine — delivered in two doses, 3 weeks apart — deeming it safe and effective.
How safe is the COVID-19 vaccine?
Paul Offit, MD, a member of the FDA advisory panel that recommended the vaccine’s use, says rigorous clinical trials of the shot identified no safety concerns, despite its sped-up production.
“These vaccines were subjected to large phase III clinical trials,” says Offit, a vaccine expert at Children’s Hospital of Philadelphia. “Regarding safety, there was an insistence by the FDA that at least tens of thousands of people be observed for 2 months after the final dose to make sure that there were no … uncommon side effects.”
Offit says the fast-tracking of the vaccine was mostly a result of the upfront financing the federal government provided, so no shortcuts were taken in verifying its safety.
“The government essentially paid for overlapping phenomena, which is to say the vaccines were mass-produced without knowing if they worked or were safe yet, so they overlapped the phase III trials with the mass production, which would never normally happen,” he says.
Gigi Gronvall, MD, an immunologist and infectious disease specialist with the Johns Hopkins Center for Health Security, agrees and says the vaccine still underwent all of the safety checks involved in any clinical trial.
“It has been tested as other vaccines and drugs have been. There were no things done differently, but the financial part made things happen faster,” says Gronvall, an associate professor at the Johns Hopkins Bloomberg School of Public Health.
How concerned should we be about adverse reactions being reported?
There is a remote chance the vaccine could cause an allergic reaction in some people within an hour of receiving the shot, the FDA says. But such reactions are likely to be mild and not life-threatening.
British regulators stoked concerns about such risks last week, after two U.K. health care workers had allergic reactions to the Pfizer vaccine. Two health care workers in Alaska also reported severe allergic reactions.
As a result, British health authorities say they will continue to investigate the two cases and monitor the vaccination program for other cases. But they also say that serious reactions to the vaccine are “very rare.”
During a meeting of an FDA advisory panel last week, experts pressed company officials on the question of allergic reactions, in light of the British cases.
Pfizer officials say there were no cases of serious allergic reactions in the clinical trial of its safety and efficacy involving nearly 44,000 participants.
The FDA panel decided against recommending that people with a history of allergic reactions to vaccines avoid the Pfizer shot — a position later echoed by the CDC.
But in greenlighting the vaccine, the FDA is requiring Pfizer to increase its monitoring for allergic reactions and submit follow-up data. That decision cleared the way for the first vaccinations to begin this week
Offit hails the FDA decision and says follow-up studies of the vaccine’s safety will put to rest any lingering concerns.