Because you look at similar cohorts at the same time. So if group A has received the vaccine, but group B has not, and they're being observed during the same time/geographical area, and the groups are sufficiently randomized otherwise, then you would expect to capture the effect of any other confounding variables.
Given the large number of people vaccinated so far, and the magnitude of the effect it's pretty safe to say that the vaccine is causing a significant reduction in hospitalizations independent from the broader background trend towards lower prevalence of the disease overall.
Sounds like cherry picking to me. Doctors know if you have been vaccinated when making this decision. I.e. perhaps 90% of people with 1 dose who are admitted are serious enough to need intensive care vs a small percentage of non-vaccinated patients admitted more often as a precaution.
I guess everyone here thinks double blind trials are for fools?
cases:mortality would be a weebit less influenced by placebo and it would be hard to reach numbers like 80%..
IMO, there's no way a significant number of discussions between doctor and patient are not going to reach different conclusions about whether to go to check in to a hospital or wait a few more days based on a significant fact like a jab 3 weeks ago.
Given the large number of people vaccinated so far, and the magnitude of the effect it's pretty safe to say that the vaccine is causing a significant reduction in hospitalizations independent from the broader background trend towards lower prevalence of the disease overall.