Thread by @jossreimer

Let’s talk about the effectiveness of the #COVID19Vaccine against severe illness. In many parts of the world there has been a surge in Delta variant cases and some recent data out of Israel is also causing some people to be concerned. (1/14)

The report out of Israel showed that out of 515 patients hospitalized with severe illness, just over half were fully vaccinated with two doses of vaccine. That sounds scary. (2/14)

Because of this, many people may think the vaccine isn’t working. That’s obviously stressful for people – but that statistic is actually really misleading. (3/14)

While the numbers from that report are accurate, you have to be extremely careful in making conclusions on vaccine effectiveness, because of the other variables that are in play with this kind of data. (4/14)

It’s important to note that nearly 80% of everyone 12 + in Israel is vaccinated. When most of your population is vaccinated, they will make up a higher proportion of hospitalization. (5/14)

Let’s use this as an example: imagine 10 people in front of you. 8 are vaccinated and 2 are not. When all 10 people are exposed to COVID, 2 of the vaccinated and 1 of the unvaccinated people become infected. (6/14)

So, in this imaginary situation 2/3 (67%) of the cases were in vaccinated people! So some people will think the vaccine is actually causing more infections. (7/14)

BUT we when look at the risk based on vaccine status, it tells a different story. Only 25% (2 out of 8) of the vaccinated people became infected but 50% (1 out of 2) of the unvaccinated did. So the infection rate was DOUBLE in the unvaccinated population. (8/14)

This is what we are seeing in Israel. Vaccinated people make up the vast majority of the population at high risk and therefore are overrepresented in hospital numbers, even though the vaccine is still very effective. (9/14)

A separate analysis ran numbers on the data from Israel and, after accounting for the vaccination rates and age, showed that the vaccines remained between 85-95% protective against severe illness. (10/14)

This second analysis also showed partial vaccination provided 75-85% effectiveness against severe disease, and that rates of severe illness were more than 3x higher in unvaccinated versus vaccinated people. (11/14)

When it comes to COVID, there will always be new studies, new statistics, new reports and new information. (12/14)

What hasn’t changed is this: There is very strong evidence that these #COVID19Vaccines continue to be highly effective in protecting against COVID illness, even in Israel. (13/14)

Getting vaccinated is the right thing to do and it *will* help protect you, your loved ones, and our communities against #COVID19. (14/14)