[Effects of vaccination status on the disease severity of patients with coronavirus disease 2019]

To evaluate the effect of 2019 novel coronavirus inactivated vaccine on the disease severity of patients with Delta variant of coronavirus disease 2019.

A retrospective analysis was performed on 704 patients with coronavirus disease 2019 infected with Delta variant who were older than 18 years old and admitted in the coronavirus disease 2019 designated hospital of Yangzhou (Subei Hospital New Area Branch) from July 2021 to September 2021. They were divided into severe (severe, critical) group and non-severe (light, ordinary) group according to the clinical characteristics of patients. According to the vaccination status, they were divided into 0-dose group, 1-dose group and 2-dose group. We evaluated the effects of vaccination on the severity of the disease and the production of antibodies, and analyzed the influencing factors leading to the severe group of coronavirus disease 2019.

The proportion of severe group in the 2-dose vaccinated group was significantly lower than that in the 1-dose vaccinated group and 0-dose vaccinated group [3.02% (7/232) vs. 9.48% (22/232), 15.83% (38/240), P < 0.05]. The time from onset to admission (day: 1.97±1.66 vs. 2.66±2.70), age (years: 45.3±12.2 vs. 63.6±17.0), direct bilirubin [DBil (μmol/L): 3.70±1.83 vs. 5.30±5.13], lactate dehydrogenase [LDH (U/L): 240.69±74.29 vs. 256.30±85.18], creatinine [SCr (μmol/L): 63.38±19.86 vs. 70.23±25.43], interleukin-6 [IL-6 (ng/L): 7.32 (1.54, 17.40) vs. 18.38 (8.83, 33.43)], creatine kinase [CK (U/L): 66.00 (43.00, 99.75) vs. 78.00 (54.50, 144.00)] and D-dimer [mg/L: 0.30 (0.08, 0.49) vs. 0.41 (0.23, 0.69)] of patients in the 2-dose group were significantly lower than those in the 0-dose group (all P < 0.05), while platelet [PLT (×10⁹/L): 176.69±60.25 vs. 149.25±59.07], white blood cell count [WBC (×10⁹/L): 5.43±1.77 vs. 5.03±1.88] and lymphocyte [LYM (×10⁹/L): 1.34±0.88 vs. 1.17±0.50] were significantly higher than those in the 0-dose group (all P < 0.05). The titer of immunoglobulin G (IgG) in the 2-dose group was significantly higher than those in the 1-dose group and 0-dose group on the 10th day after admission [U/L: 130.94 (92.23, 326.31), 113.18 (17.62, 136.20), 117.85 (33.52, 156.73), both P < 0.05], and higher than 0-dose group on the 16th day [U/L: 156.12 (120.32, 167.76) vs. 126.52 (61.34, 149.57), P < 0.05]. The proportion of complete 2-dose vaccination [10.45% (7/67) vs. 35.32% (225/637)], LYM (×10⁹/L: 1.09±0.32 vs. 1.25±0.56) and PLT (×10⁹/L: 138.55±68.03 vs. 166.93±59.70) in the severe group were significantly lower than those in the non-severe group (P < 0.05), while the time from onset to admission (day: 3.01±2.99 vs. 2.25±2.09), the length of hospital stay (day: 28±18 vs. 16±6), male proportion [77.61% (52/67) vs. 34.54% (220/637)], age (years: 69.13±12.63 vs. 52.28±16.53), DBil [μmol/L: 4.20 (3.18, 6.65) vs. 3.60 (2.80, 4.90], LDH (U/L: 310.61±98.33 vs. 238.19±72.14), SCr (μmol/L: 85.67±38.25 vs. 65.98±18.57), C-reactive protein [CRP (μmol/L): 28.12 (11.32, 42.23) vs. 8.49 (2.61, 17.58)], IL-6 [ng/L: 38.38 (24.67, 81.50) vs. 11.40 (4.60, 22.07)], CK [U/L: 140.00 (66.00, 274.00) vs. 72.80 (53.00, 11.00)] and the D-dimer [mg/L: 0.46 (0.29, 0.67) vs. 0.35 (0.19, 0.57)] in the severe group were significantly higher than those in the non-severe group (all P < 0.05). Multivariate regression analysis showed that the odds ratio (OR) of severe group was 0.430 (P = 0.010) in the 1-dose group and the 2-dose group compared with the 0-dose group. However, the risk of severe group was 0.381-fold in the 2-dose group compared with the 0-dose group [OR = 0.381, 95% confidence interval (95%CI) was 0.121-1.199] which was not statistically significant, when the age was included in the regression analysis (P > 0.05). PLT (OR = 0.992, 95%CI was 0.986-0.998) were protective factors, but older than 60 years old (OR = 3.681, 95%CI was 1.637-8.278), CK (OR = 1.001, 95%CI was 1.000-1.001), IL-6 (OR = 1.006, 95%CI was 1.002-1.010), SCr (OR = 1.020, 95%CI was 1.007-1.033) were risk factors for severe group (all P < 0.05).

Compared with the 0-dose vaccinated patients, the coronavirus disease 2019 patients infected with delta variant and fully vaccinated with 2-dose 2019 novel coronavirus inactivated vaccine had lower level of IL-6, SCr, CK and D-dimer, and higher PLT, LYM and IgG titer, who were not easy to develop into the severe condition.