The durability of immunity against reinfection by SARS-CoV-2: a comparative evolutionary study.

BACKGROUND: Among the most consequential unknowns of the devastating COVID-19 pandemic are the durability of immunity and time to likely reinfection. There are limited direct data on SARS-CoV-2 long-term immune responses and reinfection. The aim of this study is to use data on the durability of immunity among evolutionarily close coronavirus relatives of SARS-CoV-2 to estimate times to reinfection by a comparative evolutionary analysis of related viruses SARS-CoV, MERS-CoV, human coronavirus (HCoV)-229E, HCoV-OC43, and HCoV-NL63. METHODS: We conducted phylogenetic analyses of the S, M, and ORF1b genes to reconstruct a maximum-likelihood molecular phylogeny of human-infecting coronaviruses. This phylogeny enabled comparative analyses of peak-normalised nucleocapsid protein, spike protein, and whole-virus lysate IgG antibody optical density levels, in conjunction with reinfection data on endemic human-infecting coronaviruses. We performed ancestral and descendent states analyses to estimate the expected declines in antibody levels over time, the probabilities of reinfection based on antibody level, and the anticipated times to reinfection after recovery under conditions of endemic transmission for SARS-CoV-2, as well as the other human-infecting coronaviruses. FINDINGS: We obtained antibody optical density data for six human-infecting coronaviruses, extending from 128 days to 28 years after infection between 1984 and 2020. These data provided a means to estimate profiles of the typical antibody decline and probabilities of reinfection over time under endemic conditions. Reinfection by SARS-CoV-2 under endemic conditions would likely occur between 3 months and 5·1 years after peak antibody response, with a median of 16 months. This protection is less than half the duration revealed for the endemic coronaviruses circulating among humans (5-95% quantiles 15 months to 10 years for HCoV-OC43, 31 months to 12 years for HCoV-NL63, and 16 months to 12 years for HCoV-229E). For SARS-CoV, the 5-95% quantiles were 4 months to 6 years, whereas the 95% quantiles for MERS-CoV were inconsistent by dataset. INTERPRETATION: The timeframe for reinfection is fundamental to numerous aspects of public health decision making. As the COVID-19 pandemic continues, reinfection is likely to become increasingly common. Maintaining public health measures that curb transmission-including among individuals who were previously infected with SARS-CoV-2-coupled with persistent efforts to accelerate vaccination worldwide is critical to the prevention of COVID-19 morbidity and mortality. FUNDING: US National Science Foundation.

A Specialized Acute COVID-19 Outpatient Clinic at an Academic Medical Center.

Health systems are challenged to provide equitable access to coronavirus disease 2019 (COVID-19) outpatient care during the pandemic. Infected patients may have difficulties accessing regular care and rely on emergency rooms. With the goal to improve system efficiencies and access to care, Stanford launched a designated outpatient COVID-19 "Care and Respiratory Observation of Patients With Novel Coronavirus" clinic in April 2020 in which all adult Stanford patients with newly diagnosed severe acute respiratory syndrome coronavirus 2 were offered follow-up for 2-3 weeks through video, telephone, and in-person encounters. Patients were triaged into risk categories and received home pulse oximeters based on a standardized protocol. Between April 15, 2020, and March 26, 2021, the Care and Respiratory Observation of Patients With Novel Coronavirus clinic enrolled 1317 patients. The clinic provided evaluation of Patients under Investigation, management of acute COVID-19 symptoms, care for COVID-19 patients after hospital discharge, clinical advice, and opportunities for research. The authors share crucial implementation lessons related to team agility, care personalization, and resource optimization.