The clinical features and immune responses of asymptomatic individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have not been well described. We studied 37 asymptomatic individuals in the Wanzhou District who were diagnosed with RT–PCR-confirmed SARS-CoV-2 infections but without any relevant clinical symptoms in the preceding 14 d and during hospitalization. Asymptomatic individuals were admitted to the government-designated Wanzhou People’s Hospital for centralized isolation in accordance with policy¹. The median duration of viral shedding in the asymptomatic group was 19 d (interquartile range (IQR), 15–26 d). The asymptomatic group had a significantly longer duration of viral shedding than the symptomatic group (log-rank P = 0.028). The virus-specific IgG levels in the asymptomatic group (median S/CO, 3.4; IQR, 1.6–10.7) were significantly lower (P = 0.005) relative to the symptomatic group (median S/CO, 20.5; IQR, 5.8–38.2) in the acute phase. Of asymptomatic individuals, 93.3% (28/30) and 81.1% (30/37) had reduction in IgG and neutralizing antibody levels, respectively, during the early convalescent phase, as compared to 96.8% (30/31) and 62.2% (23/37) of symptomatic patients. Forty percent of asymptomatic individuals became seronegative and 12.9% of the symptomatic group became negative for IgG in the early convalescent phase. In addition, asymptomatic individuals exhibited lower levels of 18 pro- and anti-inflammatory cytokines. These data suggest that asymptomatic individuals had a weaker immune response to SARS-CoV-2 infection. The reduction in IgG and neutralizing antibody levels in the early convalescent phase might have implications for immunity strategy and serological surveys.

尚未充分描述感染严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的无症状个体的临床特征和免疫应答。我们对万州地区的37名无症状患者进行了研究，这些患者在前14天和住院期间被诊断为RT-PCR确诊的SARS-CoV-2感染，但没有任何相关的临床症状。根据政策^1，无症状者被送往政府指定的万州人民医院进行集中隔离。无症状组中病毒脱落的中位时间为19 d（四分位间距（IQR），15-26 d）。无症状组的病毒脱落持续时间明显长于有症状组（对数秩P = 0.028）。无症状组的病毒特异性IgG水平（中位数S / CO为3.4； IQR为1.6-10.7）显着降低（P 相对于急性期的症状组（中位数S / CO，20.5； IQR，5.8-38.2）= 0.005。在无症状个体中，恢复期初期，IgG和中和抗体水平分别降低了93.3％（28/30）和81.1％（30/37），而96.8％（30/31）和62.2％（ 23/37）有症状的患者。在早期恢复期，有40％的无症状个体呈血清阴性，而有症状组的12.9％呈阴性。此外，无症状的个体表现出较低水平的18种促炎和抗炎细胞因子。这些数据表明，无症状个体对SARS-CoV-2感染的免疫反应较弱。恢复期早期IgG和中和抗体水平的降低可能对免疫策略和血清学检查有影响。