Vaccines reduced hospital length of stay and fraction of inspired oxygen of COVID-19 patients: A retrospective cohort study

Few studies have focused on the evaluation of vaccine effectiveness (VE) in mainland China. This study was to characterize the VE including the frequent symptoms, laboratory indices, along with endotracheal intubation, hospital length of stay (LoS), and survival status. This retrospective cohort study included patients with COVID19 admitted to our hospital. Statistical comparisons of continuous variables were carried out with an independent Student's t-test or Mann-Whitney U test. For categorical variables, the Chi-square test and Fisher exact test were used. Multivariable regression analysis was performed to adjust the confounding factors such as age, gender, body mass index (BMI), residential area, smoking status, the Charlson comorbidity index (CCI) score, followed by investigating the effects of vaccination on critical ill prevention, reduced mortality and endotracheal intubation, LoS and inspired oxygen. This study included 549 hospitalized patients with COVID-19, including 222 (40.43 %) vaccinated participants and 327 (59.57 %) unvaccinated counterparts. There was no obvious difference between the two groups in typical clinical symptoms of COVID-19, clinical laboratory results and mortality. Multivariable analysis showed that COVID-19 vaccine obviously reduced LoS by 1.2 days (lnLoS = -0.14, 95 %CI[-0.24,-0.04]; P = 0.005) and decreased fraction of inspired oxygen by 40 % (OR: 0.60; 95 %CI [0.40,0.90]; P = 0.013) after adjusting age, gender, BMI, residential area, smoking status and CCI score. In contrast, vaccination induced reduction in the critically ill, mortality, and endotracheal intubation compared with the unvaccinated counterparts, but with no statistical differences. Vaccinated patients hospitalized with COVID-19 have a reduced LoS and fraction of inspired oxygen compared to unvaccinated cases in China.