Background Coronavirus disease 2019 (COVID-19) is a pandemic with no specific antiviral treatments or vaccines. There is an urgent need for exploring the neutralizing antibodies from patients with different clinical characteristics. Methods A total of 117 blood samples were collected from 70 COVID-19 inpatients and convalescent patients. Antibodies were determined with a modified cytopathogenic neutralization assay (NA) based on live severe acute respiratory syndrome coronavirus 2 and enzyme-linked immunosorbent assay (ELISA). The dynamics of neutralizing antibody levels at different time points with different clinical characteristics were analyzed. Results The seropositivity rate reached up to 100.0% within 20 days since onset, and remained 100.0% till days 41–53. The total geometric mean titer was 1:163.7 (95% confidence interval [CI], 128.5–208.6) by NA and 1:12 441.7 (95% CI, 9754.5–15 869.2) by ELISA. The antibody level by NA and ELISA peaked on days 31–40 since onset, and then decreased slightly. In multivariate generalized estimating equation analysis, patients aged 31–45, 46–60, and 61–84 years had a higher neutralizing antibody level than those aged 16–30 years (β = 1.0470, P = .0125; β = 1.0613, P = .0307; β = 1.3713, P = .0020). Patients with a worse clinical classification had a higher neutralizing antibody titer (β = 0.4639, P = .0227). Conclusions The neutralizing antibodies were detected even at the early stage of disease, and a significant response was shown in convalescent patients.

No abstract

Background. COVID-19 is a pandemic with no specific antiviral treatments or vaccines. The urgent needs for exploring the neutralizing antibodies from patients with different clinical characteristics are emerging. Methods.A total of 117 blood samples were collected from 70 COVID-19 inpatients and convalescent patients. The presence of neutralizing antibody was determined with a modified cytopathogenic assay based on live SARS-CoV-2. The dynamics of neutralizing antibody levels at different with different clinical characteristics were analyzed.Results. The seropositivity rate reached up to 100.0% within 20 days since onset, and remained 100.0% till day 41-53. The total GMT was 1:163.7 (95% CI, 128.5 to 208.6), and the antibody level was highest during day 31-40 since onset, and then decreased slightly. Individual differences in changes of antibody levels were observed among 8 representative convalescent patients. In multivariate GEE analysis, patients at age of 31-60 and 61-84 had a higher antibody level than those at age of 16-30 (β=1.0518, P=0.0152; β =1.3718, P=0.0020). Patients with a worse clinical classification had a higher antibody titer (β=0.4639, P=0.0227).Conclusions. The neutralizing antibodies were detected even at the early stage of disease, and a significant response showed in convalescent patients. Moreover, changes on antibody levels ware individual specific.

RationaleMedical masks are commonly used by sick individuals with influenza-like illness (ILI) to prevent spread of infections to others, but clinical efficacy data are absent.ObjectiveDetermine whether medical mask use by sick individuals with ILI protects well contacts from related respiratory infections.Setting6 major hospitals in 2 districts of Beijing, China.DesignCluster randomised controlled trial.Participants245 index cases with ILI.InterventionIndex cases with ILI were randomly allocated to medical mask (n=123) and control arms (n=122). Since 43 index cases in the control arm also used a mask during the study period, an as-treated post hoc analysis was performed by comparing outcomes among household members of index cases who used a mask (mask group) with household members of index cases who did not use a mask (no-mask group).Main outcome measurePrimary outcomes measured in household members were clinical respiratory illness, ILI and laboratory-confirmed viral respiratory infection.ResultsIn an intention-to-treat analysis, rates of clinical respiratory illness (relative risk (RR) 0.61, 95% CI 0.18 to 2.13), ILI (RR 0.32, 95% CI 0.03 to 3.13) and laboratory-confirmed viral infections (RR 0.97, 95% CI 0.06 to 15.54) were consistently lower in the mask arm compared with control, although not statistically significant. A post hoc comparison between the mask versus no-mask groups showed a protective effect against clinical respiratory illness, but not against ILI and laboratory-confirmed viral respiratory infections.ConclusionsThe study indicates a potential benefit of medical masks for source control, but is limited by small sample size and low secondary attack rates. Larger trials are needed to confirm efficacy of medical masks as source control.Trial registration numberACTRN12613000852752; Results.

High-purity and superfine high-entropy metal diboride powders, namely (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B 2 , were successfully synthesized via a facile borothermal reduction method at 1973 K for the first time. The as-synthesized powders with an average particle size of ~ 310 nm had a single-crystalline hexagonal structure of metal diborides and simultaneously possessed high compositional uniformity from nanoscale to microscale. In addition, their formation mechanisms were well interpreted by analyzing the thermodynamics of the possible chemical reactions based on the first principles calculations. This work will open up a new research field on the synthesis of high-entropy metal diboride powders.