Aim: Comparison of the course, severity and outcome between COVID 19 vaccinated and unvaccinated critically ill patients, admitted to intensive care unit (ICU).

Methods: The study is based on a retrospective observation of patients with severe and critical COVID 19 infection, conducted between January 2021 and November 2022. These patients are divided into two groups - unvaccinated (n=160) and vaccinated (n=44) with confirmed SARS COV 2 associated pneumonia.

Results: The study included 204 patients, 78.43% of them were unvaccinated and 21.57% were vaccinated against SARS COV 2.  The average age of the unvaccinated patients was 63.95±11.49, and vaccinated was 70.97±13.72 (p=0.03). 61.4% of the vaccinated were men and 38.6% - women. Among vaccinated patients 93% had completed vaccination status and 7% not fully vaccinated. 34.09% of the vaccinated patients were treated with non-invasive ventilation (NIV) and 27% with mechanic ventilation (MV) support. 70% of the unvaccinated patients were with NIV and 24.36% with MV. The average ICU stay duration in the studied unvaccinated group was 8.62±6.38 days and in the vaccinated group was 5.25±9.19 days. The mortality rate in ICU in vaccinated group is 31.8% compared with unvaccinated which is 56.88%.

Conclusions: Vaccination can reduce severity of the infection, need of ventilation support, length of hospital stay and mortality of COVID 19 in critically ill patients.