Objective: Analyzing the risk factors for pneumonia development in breakthrough cases with a history of inactivated vaccine injection is important. The present study aimed to investigate the risk factors for pneumonia development during Omicron variant infection.
Design and Methods: The clinical data were retrospectively collected from 187 patients who previously received inactivated vaccine and were infected by the Omicron variant.
Results: Among the 187 patients, 73 had 2 doses of inactivated vaccine injection and the remaining 114 had 3 doses; 19 patients had pneumonia at admission. The univariate logistic analysis showed that age, baseline platelet count, D-dimer level, and CD8⁺ T lymphocyte count were associated with pneumonia development at admission. The multivariate analysis showed that only age was the independent risk factor for pneumonia development (odds ratio = 1.046, 95% confidence interval: 1.003– 1.091, P = 0.04). With an optimal cutoff value of 46, 4.4% (4/91) patients in the age < 46 years group and 15.63% (15/96) patients in the age ≥ 46 years group had pneumonia (χ ² = 6.454, P = 0.01). Moreover, age negatively correlated with CD8⁺ T cell count, B cell count, and albumin and uric acid levels (all P < 0.01), while age positively correlated with the glucose level (P < 0.01).
Conclusion: Old age was the only independent risk factor for pneumonia development in patients with Omicron variant infection and a history of inactivated vaccine injection.
Keywords: COVID-19, glucose, Omicron, pneumonia, SARS-CoV-2