evidence: These figures come from an analysis released Friday by researchers at Brown University and Microsoft AI Health — shared exclusively with NPR — that estimates the portion of vaccine-preventable deaths in each state since COVID-19 vaccines became available at the start of 2021. [...] The total for the country is stark: Many of the nearly 1 million COVID deaths took place in 2020 before the vaccines were available. But of the more than 641,000 people who died after vaccines were available, half of those deaths could have been averted – 318,981 – had every eligible adult gotten vaccinated. And those numbers are even more striking in certain states where more than half of deaths could have been avoided. [...] The national number of vaccine-preventable COVID deaths calculated by Brown and Microsoft exceeds an earlier analysis from the Kaiser Family Foundation, which put that number at 234,000. Cynthia Cox, director of the Peterson-Kaiser Health System Tracker and a co-author of that analysis, tells NPR that differences in methodology may explain the discrepancy.