What does COVID-19 vaccine effectiveness mean?

WASHINGTON — New developments in the race to develop a vaccine for COVID-19: Pfizer and its partner, BioNTech, now say their vaccine is 95% effective, but what does that mean?

Top infectious disease expert Dr. Anthony Fauci and others are optimistic that scientists’ work could help put an end to the pandemic in 2021.

“When they say it’s safe and effective to give, I can tell you, I will take a vaccine and I will recommend to my family to also take it,” Fauci said.

We’ve heard a lot about “vaccine effectiveness” recently.

It refers to the likelihood that a coronavirus vaccine will work in a majority of patients.

Two vaccine makers, Pfizer and Moderna, announced that preliminary results from their late-stage studies suggest their experimental vaccines protect against the virus.

Moderna says its vaccine appears nearly 95% effective

, and now Pfizer is reporting similar results.

Those numbers are raising hopes around the world, but the effectiveness numbers will change as studies continue.

That’s because early calculations were based on fewer than 100 COVID-19 cases in each study.

U.S. health officials have said a coronavirus vaccine would need to be at least 50% effective before they would consider approving it for use.