We in fact know very little about the consequences of serious C19 infections in people under 50, and people in their 40s apparently make up a substantial cohort of ICU C19 patients. We also don't know the long-term health implications of a severe C19 case, and there's some evidence to suggest permanent lung damage is one possible outcome. And, even if we didn't know any of those things, avoiding the deaths of people over the age of 50 and the deaths of people of all ages with asthma and hypertension would still be a worthy reason to hit the brakes while we learn more.