High temperature, COVID-19, and mortality excess in the 2022 summer: A cohort study on data from Italian surveillances.

We aimed to assess whether the effect of high temperature on mortality differed in COVID-19 survivors and naive. We used data from the summer mortality and COVID-19 surveillances. We found 3.8 % excess risk in 2022 summer, compared to 2015-2019, while 20 % in the last fortnight of July, the period with the highest temperature. The increase in mortality rates during the second fortnight of July was higher among naïve compared to COVID-19 survivors. The time series analysis confirmed the association between temperatures and mortality in naïve people, showing an 8 % excess (95%CI 2 to 13) for a one-degree increase of Thom Discomfort Index while in COVID-19 survivors the effect was almost null with -1 % (95%CI -9 to 9). Our results suggest that the high fatality rate of COVID-19 in fragile people has decreased the proportion of susceptible people who can be affected by the extremely high temperature.