Uri Shalit Profile picture
20 Jan, 19 tweets, 8 min read
I’m seeing many discussions about the evidence for vaccine effectiveness in Israel. This is a thread with my thoughts on what we know and don’t know at this point. First some vaccination statistics:

Israel has been vaccinating at a fast pace - by today 78% of people aged 60+ have received at least 1 dose, 58% of 60+ are >14 days from their 1st dose, and 30% already received their 2nd dose.

We are all waiting to see how the vaccine effect plays out in a real-world, country-wide setting.
When considering vaccine effectiveness we should separate between two related aspects:
1) How effective are the vaccines individually? Do the trial results showing strong protection from symptomatic disease still hold when vaccines are given out not in the controlled and closely monitored setting of a clinical trial, but rather in the real world…
...where people sometimes receive 5 doses at once*, refrigeration might be imperfect, and so on.

*this happened several times
2) How effective are the vaccines as a tool to control the dangers of the virus on a national level, especially in terms of preventing healthcare systems from being overrun.
Regarding the individual-level question, the two biggest HMOs in Israel have initial reports of 33-60% reduction in infection starting from 14 days after the 1st dose.
These results are based on matching vaccinated to unvaccinated using age and other factors (at least for one of the HMOs, @clalit @RanBalicer). I cannot stress how preliminary these results are, though we are sure to hear more soon.
In addition, there is a small serological study of 100 people where strong antibody response was found, especially after 2nd dose

Regarding the national-level question, so far we see no clear sign of the vaccine effect in terms of reduced case numbers or hospitalizations. While case numbers and hospitalizations are plateauing, this can easily be due the lockdown which started two weeks ago.
Many people (me included) have been looking at the data in many different ways, including all kinds of diff-in-diff and reg.-discontinuity type analyses across ages, geography, sectors etc., but frankly I have to say that in my opinion there is no clear signal yet.
I can think of several reasons for this, echoing @joshmich thread

1. Vaccine effects take time, perhaps longer than some of us hoped. Maybe especially so for older people.
In particular. effect magnitude and how long does it takes to take hold (maybe only after 2nd dose?) might be heterogeneous, again perhaps especially for older people.
2. There's a clear trend where areas w/ higher infection rates see lower vaccination rates, despite wide availability. There's an effort to make vaccines even more easily available in these areas and convince hesitant ppl to vaccinate nonetheless.

3. The vaccines might not be as effective as we hoped, perhaps due to the new variants.
In my opinion, there's no need for alarm yet. We're still too close to the start of the vaccination drive to see strong effects, especially since we are in the middle of a lockdown which might be masking some of the effects, and because of the differential vaccine update.
I hope in the next week or two we will see clearer signs of the vaccine’s effect on a national level.

And I hope friends and colleagues who are looking closely at the Israeli data will have valuable thoughts to add
@GorfineMalka @H_Rossman @segal_eran @LittleMoiz @yuvharpaz @_lewisy @KalksteinNir @erlichya @JScholar @dvir_a @feldman_gil @GazitDoron @AvishaySpitzer

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More from @ShalitUri

18 Mar 20
We’ve noticed something that looks like a potentially important data-entry problem regarding comorbidities in the “big” China CDC report on the Epidemiological Characteristics of COVID19. This report uses data from 72,314 patient records. (1/6)
The China CDC report has the most widely used numbers I’ve seen for age and sex fatality rates. It was reported in brief form in JAMA, and fully in a China CDC weekly (link below, it loads slowly sometimes).

See numbers here.
From the report:
“† The comorbid condition variable, only includes a total of 20,812 patients and 504 deaths and these values were used to calculate percentages in the confirmed cases and deaths columns.”
Read 9 tweets

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