Thread by @DavidLat

1/ The next hot-button issue in #COVID19 debates: the relative importance of #antibodies versus T cells in #COVID_19 immune response.

(If you're thinking this should be an obscure, wonky, data-driven debate, I have one word for you: hydroxychloroquine.)

2/ Some background. Antibodies are not the only possible source of #COVID19 immunity.

Or as this interesting @NatGeo article puts it, "antibodies might not be telling the whole story when it comes to #Covid_19 immunity."

on.natgeo.com/2DpoH6V #COVID

3/ Dr. Soo Aleman of Sweden tested patients who previously tested positive for #COVID19, as well as their close contacts. She found that hospitalized patients had strong antibody and T cell responses to #COVID_19 -- no surprise there.

#COVID #coronavirus

4/ "But two-thirds of the close contacts who were asymptomatic showed a subsequent T-cell response, even though tests didn’t detect any antibodies."

"Very strange and very surprising," she said.

bit.ly/2WjAqKt #COVID19 #Covid_19 #COVID #coronavirus

5/ (Note: of these asymptomatic close contacts of #COVID19 patients who had a T-cell response but no antibodies, we don't know if they never had antibodies or if they had antibodies that then declined to undetectable levels.)

#Covid_19 #COVID

6/ Then there's the issue of "cross-reactive" T-cell immune responses or T-cell "cross immunity."

See this @NYMag article by @dwallacewells for an excellent explanation.

nym.ag/3agwbos #COVID19 #COVID_19 #COVID #coronavirus

7/ Cross immunity in a nutshell:

"You don't necessarily need to catch COVID-19 for your T-cells to know how to fight it, because previous exposure to similar coronaviruses (like the common cold) had already taught your immune systems how to respond."

8/ A caveat on cross immunity: it's not necessarily "total" immunity to #COVID19.

Instead, per @dwallacewells, it might mean "a faster immune response, a shorter period of infection, and a 'massively' reduced risk of severe illness."

nym.ag/3agwbos

9/ So why does the relative importance of antibodies versus T cells in #COVID19 immunity matter?

It could have implications for the efficacy of a vaccine, societal responses to #COVID, and the necessity/wisdom of #lockdown.

#coronavirus #COVID_19

10/ On a #COVID19 vaccine, reports of no antibodies but widespread T-cell response "raise concerns about a vaccine, since stimulating antibody production is a key strategy by which immunizations protect against disease."

on.natgeo.com/2DpoH6V

11/ On societal response/#lockdown, some argue that T-cell immunity, including cross immunity, means that we can reach effective herd immunity at a much lower threshold.

See, e.g., this thread by @JamesTodaroMD (via @SubCyberSouth):

https://twitter.com/JamesTodaroMD/status/1292873236716433416

12/ So, @JamesTodaroMD argues, #lockdown and #WearAMask ordinances don't really deserve the credit for the current success in controlling #COVID19 now enjoyed by some of the hardest-hit places (e.g., my home city of New York).

https://twitter.com/JamesTodaroMD/status/1292873250813468674

13/ And then there's the case of Sweden, which everyone loves to argue over when it comes to #COVID19 and #lockdown (or the lack thereof). Here is Dr. Todaro's take:

https://twitter.com/JamesTodaroMD/status/1292873251853684742

14/ Speaking of Sweden, Swedish doctor Sebastian Rushworth argues that T cells are much more important than antibodies for #COVID19 immunity -- but we test for #antibodies "because it is easy and cheap" (also via @SubCyberSouth):

bit.ly/33TxNDs

15/ Dr. Rushworth further argues that the reason Sweden is doing so well today is because it "ripped the metaphorical band-aid off quickly and got the epidemic over and done with in a short amount of time" (because of widespread T cell immunity).

16/ Speaking for myself, I don't have a strong view one way or the other on the relative importance of antibodies versus T cells when it comes to #COVID19 immunity; I'm still reading and educating myself.

#COVID_19 #COVID #coronavirus

17/ But I do predict that what should be a scientific, scholarly, data-driven debate about antibody versus T-cell immunity is about to become very, very politicized.

#COVID19 #COVID_19 #COVID #coronavirus #antibody #antibodies #lockdown #vaccine #vaccines

18/ Here's another interesting thread, by @trvrb (via @kaustuvs). He argues that both population immunity AND societal responses like social distancing and mask wearing are contributing to reduced #COVID19 spread.

https://twitter.com/trvrb/status/1291860659118804992