Publication date: Mar 24, 2025

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.

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