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Th17 cells have been investigated in mice primarily for their contributions to autoimmune diseases. However, the pathways of differentiation of Th17 and related (type 17) cells and the structure of the type 17 memory population in humans are not well understood; such understanding is critical for manipulating these cellsin vivo. By exploiting differences in levels of surface CCR6, we found that human type 17 memory cells, including individual T cell clonotypes, form an elongated continuum of type 17 character along which cells can be driven by increasing RORγt. This continuum includes cells preserved within the memory pool with potentials that reflect the early preferential activation of multiple over single lineages. The CCR6+cells’ phenotypes and epigenomes are stable across cell divisions under homeostatic conditions. Nonetheless, activation in polarizing and non-polarizing conditions can yield additional functionalities, revealing, respectively, both environmentally induced and imprinted mechanisms that contribute differentially across the continuum to yield the unusual plasticity ascribed to type 17 cells.

The COVID-19 pandemic is associated with decreased surgical procedure volumes, but existing studies have not investigated this association beyond the end of 2020, analyzed changes during the post-vaccine release period, or quantified these changes by patient acuity.To quantify changes in the volume of surgical procedures at a 1017-bed academic quaternary care center from January 6, 2019, to December 31, 2021.In this cohort study, 129 596 surgical procedure volumes were retrospectively analyzed during 4 periods: pre-COVID-19 (January 6, 2019, to January 4, 2020), COVID-19 peak (March 15, 2020, to May 2, 2020), post-COVID-19 peak (May 3, 2020, to January 2, 2021), and post-vaccine release (January 3, 2021, to December 31, 2021). Surgery volumes were analyzed by subspecialty and case class (elective, emergent, nonurgent, urgent). Statistical analysis was by autoregressive integrated moving average modeling.The primary outcome of this study was the change in weekly surgical procedure volume across the 4 COVID-19 periods.A total of 129 596 records of surgical procedures were reviewed. During the COVID-19 peak, overall weekly surgical procedure volumes (mean [SD] procedures per week, 406.00 [171.45]; 95% CI, 234.56-577.46) declined 44.6% from pre-COVID-19 levels (mean [SD] procedures per week, 732.37 [12.70]; 95% CI, 719.67-745.08; P .001). This weekly volume decrease occurred across all surgical subspecialties. During the post-COVID peak period, overall weekly surgical volumes (mean [SD] procedures per week, 624.31 [142.45]; 95% CI, 481.85-766.76) recovered to only 85.8% of pre-COVID peak volumes (P .001). This insufficient recovery was inconsistent across subspecialties and case classes. During the post-vaccine release period, although some subspecialties experienced recovery to pre-COVID-19 volumes, others continued to experience declines.This quaternary care institution effectively responded to the pressures of the COVID-19 pandemic by substantially decreasing surgical procedure volumes during the peak of the pandemic. However, overall surgical procedure volumes did not fully recover to pre-COVID-19 levels well into 2021, with inconsistent recovery rates across subspecialties and case classes. These declines suggest that delays in surgical procedures may result in potentially higher morbidity rates in the future. The differential recovery rates across subspecialties may inform institutional focus for future operational recovery.

The primary objective was to determine the effect of the COVID-19 pandemic on volume, demographics, and mechanisms of injury (MOI) for patients seen at an urban multidisciplinary concussion center. During the first phase of the pandemic in the United States, stay-at-home orders led to decreased group activities and required cancellation of outpatient appointments or initiation of telemedicine visits.This study was a retrospective chart review of 3500 patient electronic medical records (EMR). Patients aged 1-99 years were eligible if they had been seen at New York University Langone Health Concussion Center during March 1-December 31, 2019 (control/pre-pandemic period) or during the same period in 2020 (pandemic period). Injury date, appointment date, age, sex, and MOI were captured; statistical analyses were performed using Stata17 (StataCorp, College Station, TX).There were 48% fewer visits during the COVID-19 pandemic period compared to the 2019 control period. There was a decreased proportion of pediatric patients (15% control, 6% pandemic; p = 0.007, chi-square test). Fewer concussions were related to team sports (21% control, 5% pandemic; p 0.001), and a greater proportion were caused by bicycle accidents (4% control, 8% pandemic; p = 0.037) and assault/domestic violence (3% control, 9% pandemic; p 0.001).The relative proportions of concussion MOI, age distributions, and visit volumes were significantly associated with pre-pandemic vs. pandemic periods, suggesting that COVID-19 changed concussion epidemiology during the pandemic period. This study demonstrates how epidemiologic data may inform future resource allocation during public health emergencies.