Duration of SARS-CoV-2 Serum-Neutralizing Antibodies Against SARS-CoV-2 Dependent on the Individual.

We investigated the persistence of SARS-CoV-2-specific neutralizing antibodies in serum (CoV-2-SNAb) against the "WH-Human 1" coronavirus in 57 convalescent persons from January 2020 to January 2021. The CoV-2-SNAb response against authentic "WH-Human 1" showed a significant (p < 0.01) neutralizing high effect (≥95%) in the following manner: by 94.7% neutralization for up to 6 months, by 73.1% for up to 8 months, and by 31.7% for up to 10 months in correlation with a significant decrease in the concentration of the virus determined by SARS-CoV-2 spike protein extracellular domain and spike-receptor-binding domain (S-RBD). There was neutralizing effect (<95%) when the S-RBD optical density (OD) value was more than 1.0, showing a suitable threshold of S-RBD = 1.0 (antibody-tittering, OD). However, in some convalescent persons, no neutralizing effect (<95%) was observed although the SARS-CoV-2-specific neutralizing antibodies were bound to the S-RBD (OD >1.0). The neutralization of the virus in these cases may not involve S-RBD, but rather B- and T cell memory responses in overall immunity, using the threshold value (OD = 1.0) of S-RBD as a simple and effective method to determine the neutralization effect of the antibody efficacy and use of vaccination in combination with a standard pseudovirus neutralizing assay. We suggest that convalescent persons should contact their physicians 6-month postinfection to test the function of their serum neutralizing antibodies and determine whether administering a SARS-CoV-2 vaccine is necessary to prevent the development of severe illness in the future.

Clinical Characteristics and Prognosis of 218 Patients With COVID-19: A Retrospective Study Based on Clinical Classification.

Background: Coronavirus disease 2019 (COVID-19) is an emerging infectious disease that has spread worldwide. Methods: This was a retrospective case series involving 218 patients admitted to three tertiary hospitals in the Loudi, Shaoyang, and Xiangtan areas of China from January 21 to June 27, 2020, who were confirmed by RT-PCR to have SARS-CoV-2. The patients' clinical characteristics, laboratory results, treatments, and prognoses based on clinical classification were recorded. Poor outcome was defined as admission to an ICU, the use of mechanical ventilation, or death. Results: The patients were classified into four clinical groups based on disease severity, namely mild (10/218, 5%), moderate (146/218, 67%), severe (24/218, 11%), or critical (14/218, 6%); 24 (11%) asymptomatic cases were also included in the study. The most common symptoms were self-reported cough (162/218, 74%), fever (145/218, 67%), sputum production (99/218, 45%), and fatigue (77/218, 35%). Among the 218 patients, 192 (88%) received lopinavir/ritonavir and interferon-alpha inhalation, and 196 (90%) patients received traditional Chinese medicine. Among the severe and critical patients, 25 (11%) were admitted to an ICU with or without mechanical ventilation, and one patient died. The presence of diabetes [relative risk (RR), 3.0; 95% CI, 1.3-6.8; p = 0.007) or other comorbidities (RR, 5.9; 95% CI, 1.9-17.8; p = 0.002) was independently associated with poor outcome. To date, 20 (9%) patients have retested positive for SARS-CoV-2 RNA after recovering and being discharged. Conclusion: The majority of patients in this case series were clinically classified as having moderate COVID-19. Older patients tended to present with greater levels of clinical severity. The prognosis for patients who were elderly or had diabetes or other chronic comorbidities was relatively poor.