Thread by @gorskon

This is a very old technique by antivaxxers. During measles outbreaks pre-pandemic, antivaxxers would point to the number of fully vaccinated children getting the measles as "evidence" the MMR doesn't work, ignoring the denominators (how many unvaxxed vs. vaxxed).

https://twitter.com/angie_rasmussen/status/1415314151476453379

It would always turn out that the risk of getting measles was many times higher in the unvaxxed. Raw numbers of infections are misleading if you don't know the denominator. You have to look at the fraction of vaccinated getting infected and compare it to the fraction unvaccinated

Given how long antivaxxers have used this technique, it is utterly unsurprising that they have started using it to try to claim that #CovidVaccine doesn't work. Again, before there even was a vaccine, I (and others) were predicting that antivaxxers would do exactly this.

Calculating relative risks is even better. I'd have to look up the paper, but I seem to recall that during an outbreak the risk of getting measles among unvaccinated children was something like 23-fold higher than among vaccinated children.

Part of the reason pointing to "breakthrough infections" (or whatever you want to call them) is scary to people is that there is a mistaken belief that vaccines are 100% effective. No vaccine is 100% effective. MMR, for instance is around 95% effective.

#CovidVaccine is very effective, the mRNA varieties perhaps as effective as MMR vaccines against measles, but they are not 100% effective. Again, no vaccine is. To imply that they don't work because they are not 100% effective is the Nirvana fallacy.