How — and When — We’ll Know If a Covid-19 Vaccine Is Working

Phase 3 trials explained

Emily Mullin
Medium Coronavirus Blog
6 min readAug 13, 2020

--

Photo: ANDREW CABALLERO-REYNOLDS / Getty Images

There are more than 150 experimental Covid-19 vaccines in development right now, and a handful of those have recently entered the final stages of human testing.

Initial findings show a glimmer of promise: In early trials, these vaccines appear safe and seem to spur an immune response in the body. But how will we know that a vaccine is actually working? And how soon could that be?

Despite President Trump’s rosy predictions that a vaccine will be ready by Election Day on November 3, experts say that timeline is unlikely.

“I don’t see how that’s possible,” said Paul Offit, MD, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, during a National Press Foundation briefing for journalists on August 10. “I think that would be a mistake. You want to make sure that we have clear efficacy data before we put this vaccine out there, because there is fragile vaccine confidence in this country.”

Moderna and Pfizer kicked off late-stage trials at the end of July, with both companies hoping to enroll 30,000 people. In an Aug. 7 email from Moderna obtained by CNN, investigators said they have so far enrolled 4,536 trial subjects. Meanwhile, AstraZeneca is expected to begin a large trial…

--

--

Emily Mullin
Medium Coronavirus Blog

Former staff writer at Medium, where I covered biotech, genetics, and Covid-19 for OneZero, Future Human, Elemental, and the Coronavirus Blog.