The results show that the unvaccinated (no vaccines were available in 2020) are the most exposed to Long Covid (41.8%), compared to 16% of those who were vaccinated with three doses. From March 2020 to April 2022, the research “photographed” the state of immune system of the hospital population during the succession of different variants and the effects of the vaccination campaign arrived at the third dose and, for the most fragile, at the fourth