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Many Covid vaccine trial volunteers may soon learn whether they received a placebo or the real thing. And those in the placebo groups may be offered the actual shot in the coming weeks.

Participants from both the Pfizer and Moderna clinical trials told ClearHealthCosts this week that study organizers told them they would have the option to learn which experimental group they were in. British press outlets have reported that volunteers in the Oxford AstraZeneca vaccine trial would also have the option to learn whether they received the active vaccine or a placebo.

Here’s how the trials work: Volunteers are assigned either the actual vaccine or a placebo. Under trial stipulations, they are not told which group they are in, though many trial participants have gone public to say they felt that they had reacted to the shot — particularly the second one — or they hadn’t. Here are the experiences of several vaccine trial participants. Until the study is unblinded, they would not know if they actually got it — and thus, whether the shot they got protected them, or whether they got the placebo and thus might want an actual vaccine.

Pfizer received an emergency use authorization from the Food and Drug Administration on Dec. 11 and its vaccine is already in use. One health-care worker who is in a Pfizer trial reported that she has been told she would be unblinded. Others have been saying the same thing on social media.

One Pfizer trial participant said that she asked Pfizer trial administrators and that they told her they mailed out letters to trial volunteers sometime before Dec. 16 stating that they will be unblinded in phases, starting with healthcare workers, followed by senior citizens and those who are immunocompromised. The letter went on to say that Pfizer planned to offer those in the placebo group the real vaccine in this order.

One Moderna participant received an official letter from study organizers on Dec. 15 with the following offer:

“If you would like to know whether you have received the mRNA-1273 vaccine or placebo, then you will be offered the opportunity to be unblinded.”

The letter went on to say that, if the Moderna vaccine is granted an Emergency Use Authorization by the F.D.A., volunteers who got the placebo would be offered the chance to get the real one within two weeks of approval. That authorization is expected to come as early as this week.

Some volunteers learned their status early

The news of the official unblinding announcement comes after some volunteers reported that they had already been notified about which shot they had received by research organizations contracted by Pfizer to carry out the trial. Dr. Jon Klein, a professor and administrator at the University of Louisville School of Medicine who volunteered in the trial, said study organizers called to tell him his status earlier this month.

“I’m happy but not too surprised that I received the vaccine and not placebo,” Klein said in a Twitter private message on Wednesday. “My symptoms after the second injection were very consistent with vaccine effects.”

Klein also said he was excited to learn that the placebo group may now receive the vaccine.

Dr. Shiv Pillai, an immunologist at Harvard University, lauded Pfizer and Moderna’s plans to vaccinate all trial participants.

“It is the ethical thing to do,” Pillai said in an email. “Those on the placebo should be given the opportunity to be protected as well.”

Pfizer’s vaccine trial included over 43,000 participants while Moderna’s had over 30,000. In both studies, half of participants received a placebo.

Pillai said that unblinding the placebo group does not mean researchers will stop studying the volunteers. Vaccine recipients will still be followed for the next two years.

“The main goal now is to understand if there are side effects with time and how well immunity persists,” Pillai said. “Numerous studies are now starting on the ‘surge’ of vaccine recipients that started this week — so all needed answers will be obtained in time one way or the other.”

Virginia Jeffries

Virginia Jeffries is a journalist in New York City. Since 2020, she has reported on long...