A coronavirus vaccine may take longer than 12 to 18 months

As much of the world remains at home due to the coronavirus, a lot of people have put their hopes of a big economic reopening on a vaccine. With more than 100 vaccine candidates for Covid-19 in production, things seem to be looking up — and the conventional wisdom, often restated by White House officials, is that this medical reprieve could come within 12 to 18 months. Secretary of Defense Mark Esper outright promised that “we will deliver, by the end of this year, a vaccine at scale to treat the American people and our partners abroad.”
But some experts caution even 12 to 18 months might be optimistic for a Covid-19 vaccine: The previous record for getting a vaccine was four years, and a cliché in the field is that vaccine development is measured in years, not months.