Thread by @VincentRK

Are vaccines needed if you already had COVID?

I wrote a thread a few months ago arguing: Yes. They are.

This study just out in @NEJM provides a lot of important data nejm.org/doi/full/10.10…

1) Vaccines do provide higher and longer protection than you get from infection alone

2) The incremental benefit of vaccines over prior infection alone is particularly obvious if you had COVID >1 year ago.

But it is also seen if Covid infection was less than a year ago.

3. Prior Covid infection has 80% efficacy in preventing Covid compared to no prior Covid infection. But this efficacy drops to 70% if the Covid infection was over a year ago.

Vaccines increase both numbers. They help both.

4. The study also shows vaccine efficacy decreases over time, especially after 6 months.

We know that now from many other studies. That's why boosters are important.
Get boosted.

5. Just like efficacy of vaccines goes down with time, efficacy of prior infection immunity also goes down with time. This study shows that after one year protection goes down. This is important.

It emphasizes the need for vaccines even if you have had prior Covid.

6. This study did not look at efficacy against severe disease and deaths. That's where we have really seen the marked effect of vaccines.

So whatever extra benefit you see in this study, double that. That's the benefit that's likely with vaccines against those endpoints. IMO.

7. Vaccines were developed in a tearing hurry in the midst of an unprecedented pandemic. So yes, the optimal interval and optimal number of doses were not established. We now know boosters are needed. That's the reality. It doesn't take away the remarkable benefit from vaccines.

Here is the thread I had written in Oct 2021 where I argued why vaccines will help even if you had prior Covid.

https://twitter.com/vincentrk/status/1447967441380859908

Here is a link to the thread that shows how vaccines continue to demonstrate efficacy against the omicron variant also. This is remarkable considering the omicron variant has so many mutations and the vaccines were developed against the wild type strain in 2020.

https://twitter.com/vincentrk/status/1478944588513611777

So the bottomline is whether you had Covid or not, vaccines offer extra protection. Get the extra protection.

Get your booster if you have already been vaccinated.

The question of whether infection induced immunity is better or vaccine induced immunity is better is moot. It's not relevant. It doesn't matter.

Coz we don't want infection. Vaccine is safer. If you happened to have already had the infection, well then the vaccine adds to that