COVID-19 vaccine trial ethics once we have efficacious vaccines

Abstract

Some placebo-controlled trials can continue ethically after a candidate vaccine is found to be safe and efficacious The unprecedented effort to identify one or more safe and effective vaccines for COVID-19 includes more than 180 candidates in development ( 1 ), with at least 12 in phase 3 trials ( 2 ). The testing of so many vaccine candidates, in a pandemic of a disease for which there are to date limited treatment options, raises a critical challenge: What should researchers do if a vaccine candidate is judged to be safe and efficacious? Guidance from the U.S. Food and Drug Administration (FDA) states that in the event that a COVID-19 vaccine candidate is judged to be “safe and effective,” discussion may be necessary “to address ethical arguments to break the blind and offer vaccine to placebo recipients” ( 3 ). We consider here two questions raised by this guidance: First, if a vaccine candidate is found to be safe and efficacious in a placebo-controlled trial, should the researchers continue that trial as designed? Second, should researchers continue to test other vaccine candidates using placebo-controlled trials? These two questions are especially timely given recent announcements by Pfizer and Moderna that their vaccine candidates have been found to be efficacious in preventing symptomatic COVID-19 ( 4 , 5 ).