The United States' effort to produce a coronavirus vaccine is in full throttle, and drugmakers are now seeking hundreds of thousands of volunteers to test their experimental candidates. Writing for the New York Times, Heather Murphy addresses five things patients should know before volunteering for a coronavirus vaccine trial.

Is it ethical to infect volunteers with the new coronavirus? Experts weigh in.

1. How vaccine clinical trials works

Vaccine clinical trials have three phases, Murphy notes, and participating in a Phase 1 trial would mean you're one of the first people to receive an experimental vaccine. According to Murphy, Phase 1 vaccine trials typically focus on safety, looking to see whether the vaccine candidate causes humans to experience negative side effects. If you participate in a Phase 1 vaccine trial, researchers "[t]ypically … will monitor you and a few dozen other subjects closely after each dose, and then check in periodically for about a year," Murphy writes.

Researchers usually use Phase 2 trials to further observe any potential side effects of experimental vaccines and to see whether a vaccine candidate generates an immune response, Larry Corey, a virologist at the Fred Hutchinson Cancer Research Center and leader of the Covid-19 Prevention Network, told Murphy. These trials typically involve a few hundred participants.

But even if vaccine candidates in Phase 2 trials cause participants to generate an immune response, that doesn't necessarily mean the experimental vaccines will protect participants against infection from the targeted pathogen—in this case, the novel coronavirus.

That's where Phase 3 clinical trials come in, according to Murphy. For Phase 3 trials, researchers look to enroll up to hundreds of thousands of participants and seek to determine whether the vaccine effectively prevents infection. Researchers will administer their vaccine candidates to at least half of the participants, forming a test group. The remaining participants receive a placebo or alternative treatment and serve as the trial's control group.

In Phase 3 trials for coronavirus vaccine candidates, researchers won't expose any of the participants to the virus intentionally. Instead, researchers intend to enroll a lot of participants from locations with high numbers of coronavirus cases. The researchers will track participants in both the test and control groups to see how many contract the new coronavirus. The researchers then will try to determine whether the experimental vaccine reduced the frequency of infection or the severity of Covid-19, the disease caused by the coronavirus, among the test group when compared with the control group.

Currently, there are no ongoing trials in which participants are intentionally exposed to the novel coronavirus, Murphy writes. Clinical trials in which participants are intentionally exposed to pathogens, which are known as challenge trials, have been the subject of a long-standing debate—and they've invoked particular concern when it comes to the new coronavirus, because there currently is no proven treatment or cure for Covid-19, which can be deadly.

However, some public health experts have argued that challenge trials could speed up the vaccine development and approval processes, and researchers at Oxford University in July announced that they would soon start recruiting participants for a coronavirus vaccine challenge trial. Some drugmakers in the United States have said they, too, are considering conducting such trials.

2. You can't guarantee you'll be in a test group

Murphy notes that, because vaccine candidates are experimental, "there's no guarantee that you'll actually be protected from the coronavirus at any phase" of a vaccine clinical trial. Moreover, if you participate in a Phase 3 trial, you may end up in the control group, meaning you won't receive the vaccine candidate.

Nir Eyal, director of the Center for Population-Level Bioethics at the Rutgers School of Public Health, explained that control groups are a required to assess the effectiveness of an experimental vaccine. Without a control group, the trial would tell researchers "basically nothing," Eyal told Murphy.

3. You'll get paid—but you'll also face risks

Participants in clinical trials for coronavirus vaccine candidates will be compensated, Murphy writes, and the amount participants will receive "varies by the trial." According to Murphy, the amount can range from between a few hundred dollars to a few thousand dollars.

Daniel Hoft, director of the Saint Louis University Center for Vaccine Development, told Murphy that researchers pay trial participants to compensate them for their "time and trouble."

But Arthur Caplan, a bioethicist, warned that people who find the compensation as an "extraordinarily attractive" incentive to participate in a vaccine trial also need to consider the risks associated with receiving an experimental vaccine. "You don't want to let compensation blind you to the need to pay attention to the risks."

4. You may end up paying the costs for care if you have an adverse reaction

While participants will be compensated for taking part in a vaccine clinical trial, if they have an adverse reaction to a vaccine candidate, it's possible that they'll be on the hook for the costs of any care they receive for the reaction.

"Insurance companies will rarely pay anything if you are hurt in an experiment," Caplan said. And if the vaccine developer agrees to cover any costs related to care for an adverse reaction, they typically commit only to reimbursing a participant's health insurer for those costs, he explained.

Corey recommends that people ask trial administrators about what compensation or support they'll receive if they are harmed by the vaccine candidate.

Corey also noted that, in some instances, participants who are harmed by an experimental vaccine may be eligible for restitution under the Public Readiness and Preparedness Act or, in the case of experimental coronavirus vaccines, under the federal government's epidemic relief fund.

5. How to enroll

People looking to enroll in a coronavirus vaccine trial can visit ClinicalTrials.gov, which lists all coronavirus vaccine studies that are currently active. In addition, the National Institute of Allergy and Infectious Diseases has established the Covid-19 Prevention Network website to connect volunteers to coronavirus vaccine trials.

Further, COVID Dash—which is managed by a group of clinical researchers, doctors, and students trying to encourage people to volunteer in coronavirus clinical trials—is a portal that helps people volunteer for coronavirus-related studies throughout the world, Murphy writes.

Murphy also notes that people can visit the 1 Day Sooner website to sign up for future coronavirus vaccine challenge trials (Murphy, New York Times, 8/5).