On Tuesday, the U.S. Food and Drug Administration (FDA) signaled its resistance to President Donald Trump’s urgency for accelerated approval of a COVID-19 vaccine, while experts call for a thorough review of any vaccine before approval.

The agency also released a new guidance document, updating a previous set of guidelines it released in June.

In the new guidance, FDA authorities have outlined the requirements for even a limited clearance or approval, called Emergency Use Authorization (EUA), for a coronavirus vaccine.

The agency said in a document, “Data from Phase 3 studies should include a median follow-up duration of at least two months after completion of the full vaccination regimen to help provide adequate information to assess a vaccine’s benefit-risk profile.”

“Vaccines are complex biological products, and a EUA for a COVID-19 vaccine may allow for rapid and widespread deployment for the administration of the vaccine to millions of individuals, including healthy people,” the FDA staff said in the documents.

The FDA’s briefing document meeting, which will take place on October 22, appears to be markedly at odds with the Trump’s claim, telling Americans that “vaccines are coming momentarily.”

On Monday night, Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases (NIAID), said that there could be evidence “as early as November or December about whether one of the vaccines now in testing will work out.”

Dr. Peter Lurie, the former FDA associate commissioner for public health strategy and analysis, described the agency’s release of the new guidance as a positive development.

“It is an encouraging sign that, despite opposition from the White House, the Food and Drug Administration has effectively published guidelines for emergency release of a vaccine for COVID-19 by disclosing the advice it has been providing to individual sponsors,” Dr. Lurie said.

In a news release, Dr. Lurie said the White House had sought to keep the FDA guidance under wraps “so it could maintain the public fiction that a safe and effective vaccine could be available before Election Day or even so that it could force emergency authorization of a vaccine with more limited follow-up.”

“Even the pharmaceutical industry has been clamoring for the release of these guidelines. We all want a safe and effective vaccine to end the pandemic, and we want it sooner rather than later,” he added. “But we can’t afford for the Trump administration to bungle vaccine review the way they’ve bungled nearly every other aspect of its pandemic response.”

In a joint statement, Dr. Ross McKinney Jr., Chief Scientific Officer of the Association of American Medical Colleges (AAMC) and Dr. David Skorton, CEO of AAMC, said, “Full approval of a new vaccine or biologic requires demonstration of safety and effectiveness through a process that includes evaluation by the VRBPAC.” “Their recommendations are considered by FDA staff who ultimately have the authority to approve the new product,” they added.