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. 2025 Mar 24;170(5):88.
doi: 10.1007/s00705-025-06275-9.

Effectiveness of inactivated COVID-19 vaccine against symptom severity in hospitalized COVID-19 patients infected with the Omicron variant

Qing-Yan Ye #  1 , Zhi-Tian Jiang #  2 , Yun Jiang #  3 , Jing-Wen Cai #  4 , Zhen Zhou  4 , Jie Song  5 , Qian Wang  4 , Qi-Qi Wu  4 , Gang Zhao  6 , Jia Chen  7 , Qi-Hua Ling  8
Affiliations

Effectiveness of inactivated COVID-19 vaccine against symptom severity in hospitalized COVID-19 patients infected with the Omicron variant

Qing-Yan Ye et al. Arch Virol. .

Abstract

In this study, we analysed the outcomes of 1165 symptomatic patients infected with the SARS-CoV-2 Omicron BA.2 variant and their response to Sinovac-CoronaVac vaccination. We assessed the effectiveness of vaccination against adverse outcomes (severe, critical, or fatal cases). Of these patients, 504 (43.3%) were men, the median age was 71 years, and 391 patients (66.4%) had received the Sinovac-CoronaVac COVID-19 vaccine (Sino Pharma, Beijing, China). The percentages of severe, critical, and fatal cases were 3.9%, 2.8%, and 3.7%, respectively, with significantly lower rates among vaccinated patients (2.8% vs. 14.2%; adjusted odds ratio [aOR], 0.306; 95% confidence interval [95% CI], 0.129-0.727). Age ≥ 70 years and a CRP level > 8 mg/L were independent predictors of an adverse outcome. Out of 630 patients aged ≥ 70 years, 107 (17.0%) were vaccinated. Seven vaccinated patients (6.5%) and 94 unvaccinated patients (18.0%) experienced adverse outcomes. Multivariate analysis indicated that vaccination (OR, 0.401; 95% CI 0.162-0.991) and CRP levels > 8 mg/L (OR, 3.262; 95% CI 1.754-6.067) were independently associated with adverse outcomes in patients aged ≥ 70 years. Inactivated vaccines were effective against symptomatic and severe COVID-19. Even in symptomatic Omicron infections, full vaccination with inactivated vaccines significantly reduced the number of adverse cases, especially in patients aged ≥ 70 years. Systemic inflammation (as measured by the CRP level) was independently correlated with adverse outcomes in patients infected with Omicron BA.2.

Keywords: COVID-19; Inactivated vaccines; Infection; Omicron; Outcomes.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The ethics committee of Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, approved this retrospective cohort study. Written informed consent was waived due to the retrospective nature of the data retrieval. Conflict of interest: The authors declare that they have no competing interests.

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