Researchers around the world are racing to create a vaccine to defend people from the Covid-19 coronavirus.

And President Trump is pushing them hard, with a project dubbed Operation Warp Speed; he’s suggested we could have a vaccine in production by the end of this year or soon after.

But the CEO of the pharmaceutical giant Merck says, in effect: don’t hold your breath — it’s gonna take a while.

A bit refreshing after all some of the fake press releases we've seen from pharma and the biotechs these last few months https://t.co/t5mtorYjtJ

— Prof Peter Hotez MD PhD (@PeterHotez) May 26, 2020

Merck chief executive Ken Frazier told Britain’s Financial Times (FT) on Tuesday that he sees a 12 to 18-month schedule for developing a vaccine as too optimistic. He’s refused refused to commit the company to such a timetable.

“Our experience suggests those are very aggressive [goals] compared to other timelines for getting a safe and effective vaccine,” Frazier said.

Merck is already working on two potential coronavirus vaccines, one in collaboration with IAVI, a vaccine nonprofit that helped develop drugs to treat and prevent HIV/AIDS, reports CNBC.

Frazier also announced Tuesday that Merck is acquiring Themis, a privately held biotech company based in Austria, which is developing a vaccine based on one previously developed for measles that has proven highly effective.

Frazier said human testing of the Themis coronavirus vaccine will begin “in just a few weeks,” FT said.

But completing that testing will take time.