Sanofi and Merck are behind this group of five. But the race for a vaccine is not a winner-take-all situation. The world is expected to need vaccines from any number of manufacturers to curb the Covid-19 pandemic, and it’s likely that some that aren’t among the first to cross the finish line will have advantages the earliest vaccines do not.

“The best outcome for us is to have several across the finish line because the global need is tremendous,” said Luciana Borio, a former acting chief scientist at the Food and Drug Administration who is now vice president at In-Q-Tel, a not-for-profit investment group.

“Speed is just one parameter. And actually in the global scheme, it’s not the most important one,” said Borio, who stressed the need for safe and effective Covid-19 vaccines.

Sanofi and Merck are both known to prefer underpromising and overdelivering.