Thread by @leorahorwitzmd

My periodic reminder that WE ARE NOT GOING TO SOLVE #COVID19 THROUGH NON-VACCINE HERD IMMUNITY. For those who need more convincing, thread follows.

First, we have NEVER gotten to herd immunity without vaccine for a virus. If you are over 40, you almost certainly had chicken pox as a kid. Until vaccine in 1995, we had >4 million cases/year (& ~125 deaths) - about the same as how many kids are born each year.

In other words, EVERY NON-IMMUNE PERSON (i.e. every kid) STILL GOT IT, even though antibody rates among adults were 90-95%, and immunity is near lifelong. With circulating virus and no vaccine, most without immunity will eventually catch it even if the pop is largely immune.

Vaccines help with herd immunity (non immune people not getting sick) both because they make people immune AND because they do so without them first getting sick and spreading the virus. That helps reduce the amount of virus in circulation.

And even then, the non-immune are still vulnerable - witness big recent outbreaks of measles, mumps from letting up just a little in vaccination. (Yes, measles is more contagious than covid. But we have 10000x fewer infections and way higher immunity.) cdc.gov/measles/cases-…

Second, my guess is that natural #COVID19 immunity won’t be as durable as, say, chicken pox immunity. At least, it isn’t for seasonal cold coronavirus. So the number of non-immune people is likely always to be high even with widespread transmission. nature.com/articles/s4159…

Third, as @CDCgov recently reminded us, even if we thought it would work, we are crazy far away from widespread #COVID19 immunity - probably <10% nationally. cdc.gov/coronavirus/20…

In NYC, with highest rates of immunity in the nation, we are having an outbreak right now in the very communities that were hardest hit in the spring and that have even higher immunity rates than the rest of the city. ny1.com/nyc/all-boroug…

And finally and most importantly, trying to get to natural herd immunity - even if it were feasible - would require a gut-wrenching number of deaths and long term complications. At least 800k deaths at a conservative 0.3% IFR. We can not become a society that welcomes that.

So, if not fatalistic resignation and hope for natural immunity, what options do we have? Care for each other: mask wearing, avoidance of indoor crowds, redesign of work, making every effort to keep schools open. It’s not sexy, but it will save lives as we wait for vaccine.