To analyze the effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine on the incidence of myocardial injury after infecting Delta variant in people of appropriate age.

A total of 288 patients with SARS-CoV-2 Delta variant infection, who admitted to Nanjing Public Health Medical Center from July to August 2021, were divided into two groups according to whether or not the cases had myocardial injury: the myocardial injury group (n = 40) and the control group (n = 248). The differences of clinical data between the two groups were analyzed using the method of retrospective case-control study. The multivariate Logistic regression analysis was performed to determine the influence of related factors on the occurrence of myocardial injury in these patients. The receiver operating charac teristic (ROC) curve model was established to further analyze the clinical significance of the possible important risk factors.

There were significant differences in gender (χ² = 5.810, P = 0.016), age (t = 2.850, P = 0.005), body mass index (t = 2.316, P = 0.021), hypertension (χ² = 11.782, P = 0.001), diabetes (χ² = 6.921, P = 0.009), completion of vaccination (χ² = 7.196, P = 0.007), hypersensitive C-reactive protein (Z = 3.745, P < 0.001), interleukin-6 (IL-6) (Z = 3.649, P < 0.001), CT manifestations of inflammatory lung disease (χ² = 4.140, P = 0.042), and concomitant liver dysfunction (χ² = 9.454, P = 0.002) in two groups. The results of multivariate Logistic regression analysis showed that hypertension[hazard ratio (HR) = 2.872, 95% confidence interval (CI) (1.104, 7.471), P = 0.031], increased IL-6 [HR = 1.024, 95%CI (1.005, 1.043), P = 0.014], and concomitant liver dysfunction [HR = 2.680, 95%CI (1.046, 6.865), P = 0.040] were risk factors for myocardial injury in patients with Delta variant infection, while completion of vaccination[HR = 0.246, 95%CI (0.097, 0.623), P = 0.003] was its protective factor. The ROC curve model showed that the level of IL-6 [area under the curve (AUC) = 0.680, 95%CI (0.586, 0.773), P < 0.001] had a predictive value for myocardial injury in patients with Delta variant infection, and the optimal threshold of IL-6 was 3.69 ng/L (sensitivity 87.5%, specificity 46.0%).

Hypertension, increased IL-6 and concomitant liver dysfunction significantly raise the incidence of myocardial injury after infecting Delta variant in people of appropriate age. IL-6 can be used as a predictor for early identification of cardiovascular complications, and completion of vaccination is an effective protective factor in such population.