Monkeys, ferrets offer needed clues in COVID-19 vaccine race

The global race for a COVID-19 vaccine boils down to some critical questions about how much to rev up people’s immune systems — and whether revving it the wrong way could cause harm. Even as huge studies in people are poised to start, behind the scenes scientists are still testing ferrets, monkeys and other animals, seeking clues to those basic questions. The first animal studies trickling out show no sign of a side effect that has worried researchers. But it’s still not clear exactly how much of an immune reaction possible vaccines need to spark for real protection.