Thread by @gbrumfiel

President Trump keeps saying that sooner or later SARS-CoV-2 will "disappear."

But this idea that somehow the pandemic will burn itself out doesn't hold up. Here's why. (DEPRESSING-ISH FRI THREAD)

npr.org/sections/healt…

First, the theory: It's known as "herd immunity". If enough people catch COVID-19 and recover, and if they are immune, then the entire population will be protected. Estimates vary widely, but somewhere between 50%-80% of a given pop would need to catch COVID for this to work.

Herd immunity is real, but historically only discussed in terms of vaccination campaigns.

For example, if 95% of a population is vaccinated against measles (very contagious) then a single case cannot spread into the community.

I spoke to a lot of scientists about trying to get to herd immunity without a vaccine, and most said it just wasn't going to happen. The problem isn't in the theory, but in the practical realities around COVID-19.

The most obvious prob: a lot of people would die in the process.

That's why governments CAN'T really make it official policy. The U.K. and the Netherlands both toyed with it, but quickly realized it was a political catastrophe to officially pursue it.

Only one country pursued a strategy that COULD lead to herd immunity, and that was Sweden...

They limited gatherings and told people to be careful, but they kept businesses open. The result? Much higher death rates than Nordic neighbors, and fairly low rates of infection. They've gotten to about 6% according to serology surveys....

folkhalsomyndigheten.se/nyheter-och-pr…

It'll take time to understand why that's the case, but @devisridhar has a good theory: individuals REALLY don't want to catch COVID-19. "Nobody wants to be part of the herd."

And it turns out you CAN reduce your chances of catching COVID-19, with masks, social distancing, contact tracing and isolation.

In nations that have good systems running, that pushes infection rates lower still. It would take South Korea basically ∞ to get to herd immunity.

The final twist: some recent studies showing that individual immunity could fade with time. And there is precedent for reinfection by less dangerous coronaviruses.

Even if COVID re-infections were mild, it would make herd immunity impossible says @neil_ferguson and others...

DISCLAIMER: There is still NO scientific proof that reinfection is happening. And it may be awhile before we know for sure what happens.

But the idea that a single infection would confer immunity for ever and ever is the most optimistic scenario.

Anyway, put it all together, and pretty much all the scientists and clinicians I spoke too agreed: natural herd immunity is not how this ends.

Countries that don't contain the virus will be seen as losers, not winners. And COVID-19 will probably become endemic.

(Which @Pien_Huang will tell you, on a global scale, isn't exactly news: npr.org/sections/goats…)

NOW FOR SOME GOOD NEWS!

First, @rrichardh points out that these fading antibody studies are not a disaster.

People will probably be immune for a long time (maybe years) if they recover from COVID-19. Still doesn't solve herd immunity, but good news!

npr.org/sections/healt…

And as @aizenglobe points out, masks really really work!

High mask compliance might even help open up more of the economy.

npr.org/sections/healt…

And we are making progress! Vaccine results are promising! And rapid testing is coming! Both will be a big help, and the vaccine could help us get to a herd-immunity-like state.

npr.org/sections/healt…

npr.org/sections/healt…

So bottom line to a longer-than-I-expected thread: We can get out of this, but not by waiting around for the problem to take care of itself. Which kind of sucks, because I'm suuuppperrr lazzyy....

Masks up everyone! Onward!