Eighteen months might sound like a long time, but in vaccine years, it’s a blink. That’s the long end of the Trump administration’s time window for developing a coronavirus vaccine, and some leaders in the field say this is too fast -- and could come at the expense of safety.

The estimated time made headlines last month when Trump remarked at a televised Cabinet Room meeting with pharmaceutical executives that a vaccine could be ready in «three to four months.» There, in front of TV cameras, Dr. Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases (NIAID), poured cold water on Trump’s estimate, saying it would be more like a year to a year and a half.

Ever since, that estimate of 12-18 months has become gospel, its appearance in media stories ubiquitous. But medical experts and scientists with firsthand experience developing vaccines are skeptical.

“Tony Fauci is saying a year to 18 months -- I think that’s optimistic,” said Dr. Peter Hotez, a leading expert on infectious disease and vaccine development at Baylor College of Medicine. «Maybe if all the stars align, but probably longer.»

Dr. Paul Offit, the co-inventor of the successful rotavirus vaccine, put it more bluntly.

“When Dr. Fauci said 12 to 18 months, I thought that was ridiculously optimistic,” he told CNN. “And I’m sure he did, too.”

Vaccines development typically measured in years, not months

As the number of U.S. coronavirus deaths surges past 3,000, the pressure on the scientific community to find a vaccine is immense. In just a few weeks, the virus has jammed the gears of a robust economy and destroyed 3.3 million jobs. Fear is off the charts, and with that comes the pressure to find a fix yesterday.

“I don’t think it’s ever been done at an industrial scale in 18 months,” said Dr. Amesh Adalja, a senior scholar focused on emerging infectious disease at the Center for Health Security at Johns Hopkins University. «Vaccine development is usually measured in years, not months.»

Vaccine trials typically start with testing in animals before launching into a three-phase process.