EXPLAINER: Should vaccine volunteers now get the real thing?

Tens of thousands of Americans have volunteered to test COVID-19 vaccines, but only about half of them got the real thing during trials.

Now, with the first vaccine rollouts and a surge in coronavirus infections, experts are debating what to do about the half that got a dummy shot.

Should everyone now be offered a vaccine? Or should the two groups in the Pfizer and Moderna studies remain intact in order to collect long-term data on how well the vaccines work?

“There’s a real tension here,” said Dr. Jesse Goodman, an infectious disease specialist and former chief scientist at the U.S. Food and Drug Administration. “There’s not an easy answer.”

HOW VACCINE STUDIES WORK

New drugs, vaccines or treatments usually go through rigorous tests and evaluations before reaching regulators for approval.

For vaccines, researchers compare what happens when a large group of volunteers gets the shots, versus what happens to another large group that doesn't. They compare side effects in each group. And they measure the vaccine's effectiveness by looking at how many in each group pick up infections.

To do this fairly, researchers randomly assign participants to receive a vaccine or a dummy shot, usually a dose of salt water.

Volunteers know there’s a 50-50 chance they could be put in either group — and they are not told which group they landed in. Often, the researchers or others involved in the testing are also “blinded” and don't know either.

SHOULD TEST VOLUNTEERS BE TOLD?

About 17,000 of Moderna’s study participants received a placebo, as did about 22,000 people in Pfizer’s trial.

With the ongoing coronavirus crisis, health experts worry about leaving them in the dark and unprotected. They argue they should be given a vaccine now in recognition of their...