Thread by @ariehkovler

Thanks to vaccines, Israel looked like the first country in the world to reach herd immunity from the coronavirus. But then Delta arrived. Daily cases shot up from less than 20 to around 750 in three weeks.

Most of the daily cases in Israel are now among vaccinated people. 56% of Israelis are vaccinated, and they make up roughly the same proportion of daily cases (though there are lots of demographic confounders in that data!)

On the other hand, only 1% of daily cases are people who previously tested positive for Covid, despite this group constituting 9% of the population. Again there are confounders here, but I think the effect is probably real.

https://twitter.com/ariehkovler/status/1411970298426150912

Most of new severe hospitalised Covid patients are vaccinated, too. This isn't a surprise. ~90% of over 50s, the most vulnerable group, are vaccinated. In a population with high enough vaccination, most of the severely ill will be from the larger group of vaccinated people.

A key number is the ratio of new cases to new hospitalisations and deaths. It's too early in Israel's Delta spike to have a clear picture of that, but the UK's experience gives a good sense that there will be MANY fewer severe cases for the same level of infection.

My fuller take on this data is in this article

arieh.substack.com/p/inside-israe…

Questions I'm thinking about for Part II:

1. 'third doses' and waning protection
2. How much Delta can a vaccinated country live with?
3. With the brief mirage of full vaccine-induced herd immunity gone, what do we do now?

One point I just want to stress: Delta in a vaccinated population might be a challenge. Delta in an unvaccinated, exposed population will be a horrific nightmare like India faced.

All of you antivaxxers retweeting this thread: I hope your followers can read, even if you can't. We need to be honest about the challenges Delta poses, but the vaccine is keeping people out of hospitals, saving lives and preventing millions of deaths. Everyone should get one.

Israel's current severe Covid cases by age and vaccine status, with each group normalised per million people. This really shows the impact that the vaccines are having,

With very high vaccination, the breakthrough cases become the majority. But the very small minority of over-40s who aren't vaccinated are disproportionately vulnerable to severe disease.

Graph above was made by @AArgoetti

https://twitter.com/AArgoetti/status/1416834739911204869

Note this is n=61 and the absolute sizes of the groups are small. Eg there's almost no unvaccinated under-90s in the first place.