And even more than mentioning vaccination rate you also have to consider age distribution. Age is still a significant factor of infection chance and disease se

And even more than mentioning vaccination rate you also have to consider age distribution. Age is still a significant factor of infection chance and disease severity/outcome. If older people are more likely to be vaccinated than younger people then it skews to more breakthroughs. You can even get a simpson's paradox where people were seeing higher fatalities in overall vaccinated vs unvaccinated but is not true when you controlled for age. And these days one would probably also have to consider time since last vaccination since antibody titer wanes with time which is likely important.