Oh, the frustration!
Massachussetts data does *NOT* break down individuals by vaccine booster status. So, the reporting is “fully vaccinated” (meaning 2 does *or more*) and “not fully vaccinated”.
It is known that the 2 does series does not really protect all that well against Omicron. So, from the reporting of “breakthrough cases” — we actually can’t really tell how well the *actual* “fully vaccinated” fare against covid.
We know that 79% of MA residents have received at least the 2 shot series. We know that 56% of *those* (meaning about 44% of the entire population) have received at least 1 booster.
So, here’s the problem: I can calculate that in MA, based on the reported numbers of “breakthrough cases’, the “at least 2 does” is about 32% effective at preventing COVID-19 infections*. What I *can’t* tell is that, of those that got infected, how many of them were boosted vs how many not? We don’t know.
* Caveat: it’s possible that the vaccine isn’t preventing COVID, but there is in fact a common cause that is correlated to both vaccination and uninfection — like people actively trying to avoid COVID by not going out, etc. That is surely some part of the apparent success of vaccination. I doubt that it’s most of it.
