Covid-19 Vaccine Protection against Mortality in Patients with Oxygen: A Multicontinental Study

ABSTRACT

INTRODUCTION: The COVID-19 vaccines have effectiveness above 90% for avoiding hospitalization. However, 5% of vaccinated patients require hospitalization with a mortality ratio between 15% to 24%, similar to the one reported for unvaccinated hospitalized patients. These vaccinated patients belong to the most sensitive groups with a high comorbidity burden. The similarity in the mortality ratio between vaccinated and unvaccinated patients has been used to make claims against the vaccine's efficacy. A thoughtful analysis, taking into account the comorbidities of each group, on how vaccination protects patients with moderate or severe illness, is missing. METHOD(S) We perform a multi-continental retrospective cohort study in 111 hospitals in Spain and 37 in Argentina. We included hospitalized patients who received oxygen therapy older than 18 years with COVID-19. To assess the relation between COVID-19 vaccine status and death, we performed a logistic regression adjusting by confounders. Also, as a sensitivity analysis, we perform a propensityscore matching. Additionally, we studied the Population Attributable Risk (PAR). RESULT(S) Between January 2020 and May 2022, we included 21,479 patients, 717 (3 3%) were vaccinated. Hospitalized vaccinated patients with oxygen therapy had a higher proportion of comorbidities. The overall mortality in vaccinated patients was 20 9%, and 19 5% in unvaccinated patients. The crude Odds Ratio was 1 07 (IC95% 0 89-1 29;p=0 41), while the adjusted was 0 73 (IC95% 0 56-0 95;p=0 02) in the complete case analysis (6,352 patients) and 0 77 (CI 95% 0 54-0 97;p=0 02) in the complete dataset after multiple imputations. These observations were robust to the sensitivity analysis. The adjusted PAR reduction was 4 3% (95%CI 1%-5%). Therefore, as the death proportion in unvaccinated patients was 19 6% (95%CI 19%-20 1%), if they were vaccinated the expected death proportion would have been 15 3% (95%CI 12 9%-18%;p< 0 01). CONCLUSION(S) Even with the high protection of the COVID-19 vaccine, patients with a high burden of comorbidities will be hospitalized in future pandemic waves. In this study, we observed that the COVID-19 vaccines significantly reduce the probability of death even when lung inflammation has already been initiated, with moderate or severe COVID-19 disease.