The FDA took the unusual step Thursday in opening to the public a routine meeting with an advisory group that’s weighing in on approving the coronavirus vaccine as the agency battles public concerns about its safety as well as political pressure from President Donald Trump to approve it before the Nov. 3 election.

The Vaccines and Related Biological Products Advisory Committee, an outside group of researchers and physicians who are advising the Food and Drug Administration on whether to approve a Covid-19 vaccine, debated the standards needed to ensure a Covid-19 vaccine is safe and effective in a meeting broadcast on YouTube and C-SPAN. Those are key questions among medical experts who worry the U.S. will approve a vaccine before it has been adequately tested.

Officials at the meeting Thursday said the public forum was “critical” to build public trust and confidence in the development of potential vaccines, which are being developed in record time. FDA officials promised that any vaccine would undergo rigorous testing before being distributed to the public.

“Vaccine development can be expedited. However, I want to stress that it cannot, and must not, be rushed,” said Dr. Marion Gruber, director of FDA’s Office of Vaccines Research and Review, adding the agency would not lower its standards.

Trump has pushed the FDA to approve a drug in time to distribute by the Nov. 3 election — a daunting task even his closest advisors have said is near impossible.

“I think we should have it before the election, but frankly the politics gets involved and that’s okay. They want to play their games, it’s going to be right after the election,” Trump said in a video he posted on Twitter on Oct. 7. “The FDA has acted as quickly as they’ve ever acted in history. There’s never been a time, and no president’s ever pushed them like I’ve pushed them either, to be honest.”

The agency is approving drugs “in a matter of weeks” that used to take years, he added.

Four drugmakers backed by the U.S. are still conducting their late-stage trials, and medical experts don’t expect to see trial data needed for FDA authorization until later this month at the earliest.

Because of the pandemic, U.S. health officials and researchers have been accelerating the development of vaccine candidates by investing in multiple stages of research even though doing so could be for naught if the vaccine ends up not being effective or safe.

The FDA, under pressure from the White House, has faced skepticism from medical experts that the vaccine approval process could be influenced by politics, not science.

Earlier this month, the FDA laid out updated safety standards for Covid-19 vaccine makers. The standards, posted in a document on the FDA’s website, would almost certainly prevent the introduction of a vaccine before the presidential election on Nov. 3.

The FDA had indicated it would approve a vaccine that’s safe and at least 50% effective. The flu vaccine, by comparison, generally reduces people’s risk of getting influenza by 40% to 60% compared with people who aren’t inoculated, according to the Centers for Disease Control and Prevention. FDA Commissioner Dr. Stephen Hahn has previously said the agency wouldn’t authorize a vaccine that’s not safe, even if it is fairly effective.

The FDA has also said it would track vaccines for years after they are authorized.

Dr. Doran Fink, deputy director of the FDA’s Division of Vaccines, said at the meeting Thursday afternoon that widespread deployment of a weak Covid-19 vaccine could result in more harm than good. He said the potential vaccine could end up providing a “false sense of security” that interferes with measures to reduce transmission.

It could also “interfere with the development and evaluation of potentially better vaccines that could have a greater impact on the Covid-19 pandemic,” he warned. “Without sufficiently stringent criteria, a Covid-19 vaccine candidate could be declared effective just by chance. And the risk of declaring a weakly effective vaccine and deploying a weakly effective vaccine increases as the number of vaccines being evaluated in phase three trials increases.”

Dr. Hilary Marston, medical officer and policy adviser for pandemic preparedness at the National Institutes of Health, said Thursday that the regulatory hold for AstraZeneca and pause for Johnson & Johnson are signs that safety measures put in place are working.

“Adverse events are expected to happen in these vaccine trials, both in the vaccine and placebo group,” she said. “We are finding these events because we are specifically looking for them.”