Objectives: To investigate antibody production in asymptomatic and mild COVID-19 patients. Methods: Sera from asymptomatic to severe COVID-19 patients were collected. Microneutralization (MN), fluorescence immunoassay (FIA), and enzyme-linked immunosorbent assay (ELISA) were performed. Results: A total of 70 laboratory-confirmed COVID-19 patients were evaluated, including 15 asymptomatic/anosmia, 49 mild symptomatic, and 6 pneumonia patients. The production of the neutralizing antibody was observed in 100% of pneumonia, 93.9% of mild symptomatic, and 80.0% of asymptomatic/anosmia groups. All the patients in the pneumonia group showed high MN titer (≥1:80), while 36.7% of mild symptomatic and 20.0% of asymptomatic/anosmia groups showed high titer (p < 0.001). Anti-SARS-CoV-2 antibodies could be more sensitively detected by FIA IgG (98.8%) and ELISA (97.6%) in overall. For the FIA IgG test, all patients in the pneumonia group exhibited a high COI value (≥15.0), while 89.8% of mild symptomatic and 73.3% of asymptomatic/anosmia groups showed a high value (p = 0.049). For the ELISA test, all patients in the pneumonia group showed a high optical density (OD) ratio (≥3.0), while 65.3% of mild symptomatic and 53.3% of asymptomatic/anosmia groups showed a high ratio (p = 0.006). Conclusions: Most asymptomatic and mild COVID-19 patients produced the neutralizing antibody, although the titers were lower than pneumonia patients. ELISA and FIA sensitively detected anti-SARS-CoV-2 antibodies.

中文翻译：

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与肺炎性COVID-19患者相比，无症状和轻度COVID-19患者中和抗体的产生。

目的：探讨无症状和轻度COVID-19患者的抗体产生情况。方法：收集无症状至严重的COVID-19患者的血清。进行了微中和（MN），荧光免疫测定（FIA）和酶联免疫吸附测定（ELISA）。结果：共评估了70例实验室确认的COVID-19患者，包括15例无症状/失眠，49例轻度症状和6例肺炎。在100％的肺炎，93.9％的轻度有症状组和80.0％的无症状/失眠组中观察到中和抗体的产生。肺炎组的所有患者均显示高MN滴度（≥1：80），而轻度症状组的36.7％和无症状/失眠组的20.0％均显示高滴度（p<0.001）。总体而言，FIA IgG（98.8％）和ELISA（97.6％）可以更灵敏地检测到抗SARS-CoV-2抗体。对于FIA IgG测试，肺炎组的所有患者均表现出较高的COI值（≥15.0），而轻度有症状组的89.8％和无症状/失眠症组的73.3％均具有较高的COI值（p = 0.049）。对于ELISA测试，肺炎组的所有患者均显示出高的光密度（OD）比率（≥3.0），而轻度有症状的65.3％的患者和无症状/失眠的53.3％的患者具有较高的比率（p = 0.006）。结论：尽管滴度低于肺炎患者，但大多数无症状和轻度COVID-19患者均产生中和抗体。ELISA和FIA敏感地检测到抗SARS-CoV-2抗体。