evidence: The share of COVID-19 deaths among those who are vaccinated has risen. In fall 2021, about 3 in 10 adults dying of COVID-19 were vaccinated or boosted. But by January 2022, as we showed in an analysis posted on the Peterson-KFF Health System Tracker, about 4 in 10 deaths were vaccinated or boosted. By April 2022, the United States Centers for Disease Control and Prevention (CDC) data show that about 6 in 10 adults dying of COVID-19 were vaccinated or boosted, and that’s remained true through at least August 2022 (the most recent month of data). [...] CDC and other researchers have shown that protection from COVID-19 vaccines can diminish, or wane, over time and booster doses are needed to maintain a robust immune response. Although the data we use in this analysis are not broken out by time since last vaccination, given the plateauing vaccination rate, it is likely that many of the vaccinated people who died of COVID-19 had the primary series or a booster many months or even over a year earlier, meaning they were less protected against severe illness than they once were.