The US Food and Drug Administration will look closely at vaccine clinical trial data to understand how coronavirus vaccines will work for various subsets of the population, FDA Commissioner Dr. Stephen Hahn said Tuesday.

“It’s not as easy as saying the top line results are X percent effective and X percent side effects,” said Hahn. “Let's look at these groups, let's look at side effects and let's look at efficacy in each of these groups.”

“When we go through the 44,000 patient data lines that are in these clinical trials, we have to ask those questions. We have to examine it and crunch the data, looking at subsets of patients,” he added. 

If a vaccine does not appear to work for a certain portion of the population, the FDA will say so, Hahn said. 

“If we don't have data to support the use of a vaccine, we're going to come out and say that,” Hahn said. “And then we're going to have to make some decisions about that in the emergency use authorization process.”

Hahn said the FDA will be looking at the data to understand how these vaccines work for pregnant women, children, those with existing health conditions and people from minority communities. 

“We did not require a pregnancy test for entry into the clinical trials, which means that you know when we look at the data there are likely going to be women of childbearing age who have gotten pregnant,” Hahn said. “Will that be enough data for us to have confidence in say, pregnant women should be vaccinated? I think that's something that we'll have to take a look at. I think it's unlikely, but we need to look at the data.”