DALLAS (CBSDFW.COM) –  As President Donald Trump pushes for a COVID-19 vaccine to be ready before the election, the top official for the Food and Drug Administration is not making any prediction on when a vaccine could be approved.

“Everybody in America wants a vaccine that is safe and effective and as quickly as possible,” said FDA Commissioner Stephen Hahn. “We have urgency but we are not going to cut any corners in respect to our review of it.”

As three potential vaccines enter the final stage of trials, public skepticism about getting a vaccine is growing.

In a recent CBS News poll, just 21% of voters nationwide say they would get a vaccine as soon as one becomes available. This is down from 27% when voters were asked in July.

Meanwhile, health officials estimate at least 60% of Americans would need to get a vaccine in order create a “herd immunity”. Epidemiologists say a “herd immunity” is what’s needed to end this epidemic.

Hahn told the CBS 11 I-Team he is fully aware of the challenge.

“It’s why the FDA has been transparent about what information we would need to see from a vaccine, “ Hahn said. “The bottom line is I can promise you we will not cut corners and we will use science and data to make our decision.”

FDA Commissioner Stephen Hahn addresses the media during a press conference in James S. Brady Briefing Room at the White House on on August 23, 2020 in Washington, DC. (Photo by Pete Marovich/Getty Images)

Before a vaccine could become available to public, it would need to be approved by the FDA as well as an independent review board.

Hahn said along with demonstrating it is safe to use, a vaccine would need to show that it prevents the disease or decreases its severity in at least 50% of people who are vaccinated.

Tuesday, nine pharmaceutical companies issued a letter pledging to fully vet their COVID-19 vaccines before asking for FDA approval.