Do you want to be a vaccine volunteer?

Maybe you are an altruist looking for a way to help fight the coronavirus. Maybe you are hoping to be among the first to try an experimental vaccine. Or maybe you are just bored or could use a few hundred dollars.

Whatever your reasons, scientists, bioethicists and current volunteers say participating in a vaccine trial can be meaningful. And without hundreds of thousands of volunteers, there will be no vaccine for anyone.

But you may be surprised by the commitment and risks that a trial entails. Here’s what you need to know.

How do I find a trial?

A number of sites maintain lists of coronavirus vaccine trials. The Covid-19 Prevention Network site, created by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, helps connect volunteers to phase three studies.

Right now, for example, Moderna is looking to enroll around 30,000 volunteers. ClinicalTrials.gov also lists Covid-19 vaccine studies at different phases.

What do these different phases mean?

There are three primary phases of a vaccine trial. A phase one trial is focused on safety. If you participate, you are likely to be among the first humans to try the vaccine. Researchers will want to track whether it affects you negatively, such as making you feverish or dizzy. Typically they will monitor you and a few dozen other subjects closely after each dose, and then check in periodically for about a year.

At the time you receive the vaccine, the developer won’t know if it prevents Covid-19. And even if it does, there’s little chance you’ll get the right amount. Still, phase one trials are appealing to some volunteers because clinicians can sometimes assure all subjects that they’ll get the experimental vaccine, not an inactive placebo.

Phase two is bigger and typically involves a few hundred people. At this point, researchers are still watching for side effects, but they are also examining whether their vaccine is generating an immune response, said Dr. Larry Corey, a virologist at the Fred Hutchinson Cancer Research Center and the leader of the Covid-19 Prevention Network.

If you think about a vaccine developer’s desired immune response like a bar that a pole-vaulter needs to clear to move to the next round, “you want to see that you got over the bar,” he said. To extend the metaphor, the pole-vaulter won’t know if clearing that bar was enough to win, he said. Just because a vaccine has generated an immune response doesn’t mean it was sufficient to protect anyone, he said.

Only a phase three trial allows researchers to study if their vaccine works. They do this by enrolling tens of thousands or hundreds of thousands of volunteers, giving one-half of the group to two-thirds of them the vaccine and giving the rest a placebo or an alternative treatment. They do not expose anyone to the coronavirus, but they try to enroll a large enough group in locations with enough cases that they can bank on some people getting infected in the normal course of their lives. They then evaluate whether the vaccine reduced the frequency of acquiring the infection and lessened the severity of the disease in the test group, Corey said.

How do I increase my chance of early access to an experimental vaccine?

There’s no guarantee that you’ll actually be protected from the coronavirus at any phase of a vaccine trial, no matter how hyped the product has been. By a phase three trial, of course, there’s more to suggest that it works than a phase one trial. But you might not get the vaccine at all. It might be an inactive placebo or an alternative intervention.

Researchers have to give these to some subjects to create a control group, said Nir Eyal, director of the Center for Population-Level Bioethics at the Rutgers School of Public Health.

“Otherwise what do you compare the results to?” Eyal asked.

During the Ebola outbreak, there was a push to try to run efficacy trials without a control group, he said. But eventually most researchers came around to the idea that, without a control group, a study would tell them “basically nothing” because — as with the coronavirus — its “spread is mercurial and very different in different areas at different times.”

How much will I get paid?

It could be a few hundred or a few thousand dollars. It varies by the trial.

“What you are doing is providing compensation for time and trouble,” said Dr. Daniel Hoft, director of the Saint Louis University Center for Vaccine Development.

Organizers try to avoid creating a financial incentive. So even if they could pay much more, they don’t.

“If the money seems extraordinarily attractive to you, think again,” said Arthur Caplan, a bioethicist. “You don’t want to let compensation blind you to the need to pay attention to the risks.”

If my health is harmed because of a trial, who pays for my care?

Let’s say that you are adversely affected by an experimental vaccine. You might assume that the vaccine developer will cover your health care costs. But typically the developer only commits to reimbursing your insurance company, Caplan said.

“Insurance companies will rarely pay anything if you are hurt in an experiment,” he said. So ask a lot of questions first. “If I get injured, what happens?” is among those he recommends.

Corey added that in some cases, the institute running the trials or the US government’s pandemic relief fund, known as the Public Readiness and Preparedness Act, might cover those costs.

What if I’m willing to be infected with the coronavirus to speed up the science?

Across the world, a lively debate is underway about that.

This type of vaccine research is called a “challenge trial,” which entails giving volunteers a vaccine, then deliberately exposing them to the virus to see if they end up infected.

The approach is controversial because Covid-19 has no cure and can be fatal. But it is also tantalizing because it promises to dramatically speed up research.

In mid-July, scientists at Oxford University announced that they would soon begin recruiting volunteers for such a trial. In the United States, a handful of vaccine developers have cautiously signaled they are open to a similar path eventually.

Eyal believes that the most ethical way to conduct these trials is to focus on young, healthy volunteers who meet criteria that suggest they’d be unlikely to develop a severe case of Covid-19. There are no guarantees, however, which is why some experts are adamantly opposed to challenge trials.

But if you are not deterred and want to help advance the science, the site 1 Day Sooner invites people to sign up for future challenge trials. As of last week, the site ticker showed that more than 32,000 people from 140 countries were ready to volunteer.