Thread by @erlichya

The Israeli MoH released some results about the effectiveness of the booster to tame infection rate.
Behavior or immunity or both?

A short technical thread with interesting results.
🧵🧵🧵

Israel does not conduct an RCT for the third dose. Thus, the main analysis for booster-VE is comparing the cases in boosted vs 2nd dosed as a proxy for increased protection. But boosted individuals might be ⬆️covid19-worried, leading to lower ⬇️exposure.

To mitigate that, the MoH adjusted for basic demography and calendar day of infection and reported the graph below. Y-axis: Booster vs 2nd dose fold protection as a function of days from booster.
But there is something weird...🧐

Check out the blue arrow. The booster is super effective 1 day after the jab and it starts to exponentially drop until day 6 before going up! How can it be? From immunological perspective, your memory cells just started working after the first day...

Here is my theory: the booster can create covid-like symptoms and people know that. So if a person feels bad the day after, he would say to himself: "Haim, relax. It is just the booster" and not get tested. Same thing if they have symptoms at the 2nd day but to a smaller extent.

and the process of delay in testing continues for a few days. This behavioral effect is so strong that it easily creates VE-booster of 2x-6x improvements in the first few days, which quickly wanes. The basic adjustments of the MOH are not enough to such behavioral diff.

So I am happy to see the increase in the VE-booster in later days and SURE that it does improve the situation.

However, it is clear that not all biases were addressed in this analysis.

For instance, if 10% of people felt like a wreck after the booster and stayed home, exposure will go down; if people who completed the 13th day can be the most covid-worried, exposure⬇️. Again, I do think booster WORKS but would wait for more final numbers.