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Long-Term COVID-19 Vaccine Studies Hampered As Placebo Recipients Get Real Shot

ARI SHAPIRO, HOST:

Tens of thousands of people who volunteered to participate in the Pfizer and Moderna COVID-19 vaccine studies are still participating in follow-up research, though that's somewhat hampered because many people who had been given a placebo shot opted to take the vaccine instead. NPR science correspondent Richard Harris reports on what's left to learn and what information will be harder to get.

RICHARD HARRIS, BYLINE: A mix of altruism and self-interest drove people to volunteer to take experimental COVID vaccines. Karen Mott, a 56-year-old job counselor who lives in the Kansas City area, says she signed up because she wanted to do her part to end the pandemic.

KAREN MOTT: I've been taking prescription medicine for the last 25 years. And somebody has done this type of stuff before for me, so I felt it was kind of my way of giving back.

HARRIS: Mott got a strong reaction to the second shot, so she correctly guessed that she had received the vaccine, not the placebo. And she was sad to read that one of the volunteers in the placebo group did die of COVID.

MOTT: I keep thinking about that, you know, just, why am I one of the lucky ones? And I think that makes me feel like, yeah, I need to continue providing the information that we need.

HARRIS: So when the clinic summoned her in January and offered to reveal her actual vaccine status, which is called unblinding, it was an easy call for her.

MOTT: And I chose, you know, please unblind me and that I want to stay in the study to provide additional data for you guys.

HARRIS: Vaccine scientists hope that the volunteers will stay in the study for two years. Participants provide periodic nose swabs and sometimes saliva samples to see if they've been infected. And they also give blood so scientists can better understand how the vaccine is providing protection. Mott was one of about 650 volunteers who took the experimental Moderna vaccine at a company called Johnson County Clinical Trials (ph) in Lenexa, Kan. Dr. Carlos Fierro, who runs the study there, says every participant was called back after the Food and Drug Administration authorized the vaccine.

CARLOS FIERRO: During that visit, we discussed the options, which included stay in the study without receiving the vaccine. And amazingly, there were people - a couple of people who chose that.

HARRIS: He suspects those individuals got spooked by rumors about the vaccine. But everybody else who had the placebo shot went ahead and got the actual vaccine. So now Fierro has essentially no comparison group left for the ongoing study.

FIERRO: It's a loss from a scientific standpoint. But given the circumstances, I think it's the right thing to do.

HARRIS: People signing up for these studies were not promised special treatment. But once the FDA authorized the drugs, vaccine developers decided to offer the shots. Dr. Steven Goodman at Stanford University says losing those control groups makes it more difficult to answer some important questions about COVID vaccines.

STEVEN GOODMAN: So we don't know how long protection lasts. We don't know the efficacy against variants, for which we desperately need a good control arm. And we also don't know if there are any differences in any of these parameters by age or race or infirmity.

HARRIS: Goodman is also thinking about what future studies will look like, considering the ethics of providing a placebo to people when there are effective vaccines. Participants might have to be in groups that are not currently eligible for a vaccine or who live in other parts of the world where vaccines simply aren't available. And he says the appearance of virus variants is a wild card.

GOODMAN: It may really scramble things up because there are certain variants where the efficacy of all vaccines might be so low that we're basically back to zero and that we might have to go back to placebo-controlled trials. It's hard to know.

HARRIS: That's the worst-case scenario. Vaccines currently in use in the United States seem to be at least partially effective against current variants, but worse variants could be on the horizon.

Richard Harris, NPR News. Transcript provided by NPR, Copyright NPR.