Effects of Booster Vaccination on Post-Treatment Oxygen Deterioration in Hospitalized Mild-to-Moderate COVID-19 Japanese Patients with comorbidities During the Omicron Wave.

Publication date: Jun 26, 2025

Although the emergence of the Omicron variant has decreased overall mortality from Coronavirus Disease 2019 (COVID-19) compared to the Delta variant, elderly individuals with comorbidities remain at increased risk of adverse outcomes. While vaccination and antiviral treatments have reduced the severity of COVID-19, data on the impact of booster vaccination on post-hospitalization oxygen deterioration in the Japanese population remain limited. We conducted a retrospective study of hospitalized mild-to-moderate COVID-19 Japanese patients during the Omicron variant wave (December 2021 to October 2022). Both vaccinated and unvaccinated patients were included and categorized into three groups based on their vaccination status: unvaccinated (0-1 vaccine dose), primary series (2 vaccine doses), and booster group (3-4 vaccine doses). Demographic and clinical data were collected, and the frequency and time to post-hospitalization oxygen deterioration were evaluated among the three groups. A total of 596 patients were analyzed (141 unvaccinated, 180 primary series, and 275 booster group). The booster group showed significantly lower rates of oxygen deterioration and a longer time to deterioration compared to the other groups, despite being older and having more comorbidities. A multivariate analysis, adjusted for age and gender, revealed that booster vaccination was significantly associated with a reduced risk of oxygen deterioration after initial treatment. Similar results were observed in the subgroup analysis of elderly patients aged 65 years and older. Our study demonstrated the effectiveness of booster vaccination on preventing post-treatment oxygen deterioration in hospitalized mild-to-moderate COVID-19 Japanese patients with comorbidities during the Omicron wave.

Semantics

Original Article