If Americans fail to follow health guidelines, the nation could top 400,000 coronavirus-related deaths this winter, Dr. Anthony Fauci said Tuesday.

Speaking at a virtual event hosted by American University, Fauci, who heads the National Institute of Allergy and Infectious Diseases, said, “If we don’t do what we need to in the fall and winter, we could have 300,000 to 400,000 COVID-19 deaths.”

According to the latest figures from Johns Hopkins University of Medicine, more than 210,000 in the U.S. have died from the coronavirus, more than any other nation in the world. Brazil ranks second, with more than 147,000 deaths.

Globally, the pandemic has killed more than 1 million.

The U.S. has reported 7.5 million confirmed coronavirus cases, also the world’s highest, followed by India’s 6.7 million cases. More than 35 million cases of the coronavirus have been reported since the virus began.

On Tuesday, the Food and Drug Administration released updated safety standards for makers of COVID-19 vaccines, clearing the way for requirements that are widely expected to prevent the introduction of a vaccine before Election Day.

In the new guidelines posted on its website, the FDA said vaccine makers should follow trial participants for at least two months to rule out any major side effects before seeking emergency approval. That standard had been a sticking point between the FDA and White House officials, who said it could unreasonably delay the availability of COVID-19 vaccines.

President Donald Trump has repeatedly insisted a vaccine could be authorized before Nov. 3, even though top government scientists working on the effort have said that timeline is unlikely. On Monday, Trump said vaccines are coming “momentarily” in a video recorded after he returned to the White House following a three-day hospitalization for his own coronavirus diagnosis.

FDA Commissioner Stephen Hahn said in a statement that he hoped the guidelines would help “the public understand our science-based decision-making process that assures vaccine quality, safety and efficacy.”

The requirements are aimed at companies seeking rapid approval through the FDA’s emergency authorization pathway. That accelerated process, reserved for health emergencies, allows medical products onto the market based on a lower bar than traditional FDA approval. But the FDA has made clear only vaccines that are shown to be safe and effective will be authorized for the coronavirus.