HIGHLIGHTSd Cross-sectional study of 44 hospitalized COVID-19 patients d RBD-specific IgG responses detectable in all patients 6 days after PCR confirmation d Neutralizing titers are detectable in all patients 6 days after PCR confirmation d RBD-specific IgG titers correlate with the neutralizing potency

28SARS-CoV-2 is currently causing a devastating pandemic and there is a pressing need to 29 understand the dynamics, specificity, and neutralizing potency of the humoral immune response 30 during acute infection. Herein, we report the dynamics of antibody responses to the receptor-31 binding domain (RBD) of the spike protein and virus neutralization activity in 44 COVID-19 32 patients. RBD-specific IgG responses were detectable in all patients 6 days after PCR 33 confirmation. Using a clinical isolate of SARS-CoV-2, neutralizing antibody titers were also 34 detectable in all patients 6 days after PCR confirmation. The magnitude of RBD-specific IgG 35 binding titers correlated strongly with viral neutralization. In a clinical setting, the initial analysis of 36 the dynamics of RBD-specific IgG titers was corroborated in a larger cohort of PCR-confirmed 37 patients (n=231). These findings have important implications for our understanding of protective 38 immunity against SARS-CoV-2, the use of immune plasma as a therapy, and the development of 39 much-needed vaccines. 40 41

SARS-CoV-2 has caused over 100,000,000 cases and almost 2,500,000 deaths globally. Comprehensive assessment of the multifaceted antiviral Ab response is critical for diagnosis, differentiation of severity, and characterization of long-term immunity, especially as COVID-19 vaccines become available. Severe disease is associated with early, massive plasmablast responses. We developed a multiplex immunoassay from serum/plasma of acutely infected and convalescent COVID-19 patients and prepandemic and postpandemic healthy adults. We measured IgA, IgG, and/or IgM against SARS-CoV-2 nucleocapsid (N), spike domain 1 (S1), S1-receptor binding domain (RBD) and S1-N-terminal domain. For diagnosis, the combined [IgA 1 IgG 1 IgM] or IgG levels measured for N, S1, and S1-RBD yielded area under the curve values $0.90. Virus-specific Ig levels were higher in patients with severe/critical compared with mild/moderate infections. A strong prozone effect was observed in sera from severe/critical patients-a possible

IntroductionThe Choosing Wisely guidelines advise against ordering routine blood tests for hospitalised patients unless they change management. Unnecessary testing can lead to adverse effects (eg, iatrogenic anaemia, poor sleep quality, risk for infections and increased cost of care).MethodsAn 8-week quality initiative aimed at reducing unnecessary blood tests was implemented in three internal medicine resident inpatient services. The initiative included a 30 min educational session, reminders prior to rotation and midrotation and posters in work areas that displayed lab pricing and urged judicious testing. Residents were encouraged to justify the purpose of ordering tests in their daily progress notes. Attending physicians were made aware of the initiative. Preintervention and postintervention time points were used to compare key metrics. A >10% decrease between time periods was used as an evaluation criterion.ResultsThere were 293 patient records reviewed in the preintervention period and 419 in the postintervention period. The two groups were similar in terms of age and gender. Median blood test count (complete blood count/basic metabolic profile/comprehensive metabolic profile) decreased from 4 to 2 tests per patient per day (50 % decrease) after the intervention. The median length of hospital stay decreased from 4.9 to 3.9 days (21% decrease). A decreased percentage of people requiring transfusions was also noted (2016: 6.1%, 2017: 2.9%).ConclusionThe frequency of unnecessary routine blood tests ordered in the hospital can be decreased by educating resident physicians, making them cost conscious and aware of the indications for ordering routine labs. Frequent reminders are needed to sustain the educational benefit.