An Independent Analysis of a Retrospective Cohort of 30,423 Covid-19 Patients Treated at IHU-Mediterranean in Marseille, France: Part 2, a Real-life Assessment of Covid-19 Vaccination Efficacy

Author(s): Valere Lounnas, Eleftherios Gkioulekas, Marc Rendell, Alexis Lacout, Xavier Azalbert, Christian Perronne

A cohort of 30,423 Covid-19 patients treated between March 2020 and December 2021 at the IHU-Méditerranée Infection in Marseille (France) was retrospectively analyzed in terms of treatment attempted and disease worsening factors to quantify vaccination efficacy with respect to the composite endpoint of transfer to intensive care unit or death, within a couple of months (56 days) from admission. Within limitations of the data and of the models, after adequate adjustment for sampling biases, multivariate logistic regression analyses were performed to determine unadjusted and adjusted odds ratios (ORs) for the subset of patients admitted after the Covid-19 vaccination program was started early 2021 (16,063 pts) (vaccination unadjusted OR = 0.498, 95%CI = [0.313 ; 0.794], p = 0.003 and adjusted OR = 0.462, 95%CI = [0.307 ; 0.670] , p < 0.001). Statistically significant interactions (p < 0.05) were detected between vaccination and some covariates : favorable with the virus variant Delta and possibly obesity as well (p=0.084), and unfavorable with age > 89 years, Covid-19 disease severity, immunodeficiency and possibly chronic obstructive pulmonary disease (COPD) as well (p=0.072), confirming its capacity to worsen the Covid-19 disease condition not only in some cases of severe underlying chronic illness but also in the elderly patients and when the disease severity necessitated patient's hospital admission. Additionally, sensitivity analysis showed that vaccination had no efficacy below 50 years of age (adjusted OR = 1.35; 95%CI = [0.09; 8.84], p = 0.781).