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Introduction: The COVID-19 pandemic caused by the SARS-CoV-2 virus greatly affected healthcare workers and healthcare systems. It also challenged schools and universities worldwide negatively affecting in-person education. We conducted this study is to assess the evolution of SARs-CoV-2 virulence over the course of the pandemic., Methods: A combined cohort of University students in Spain and HCWs from the two hospitals in Spain, and one healthcare system in the Greater Boston area was followed prospectively from March 8th, 2020, to January 31st, 2022 for diagnosis with COVID-19 by PCR testing and related sequelae. Follow-up time was divided into four periods according to distinct waves of infection during the pandemic. Severity of COVID-19 was measured by case-hospitalization rate. Descriptive statistics and multivariable-adjusted statistics using the Poisson mixed-effects regression model were applied. As a sensitivity analysis, information on SARS-CoV-2 RNA in wastewater and COVID-19 deaths through May 30, 2023 from the Boston area was collected., Results: For the last two periods of the study (January 1st to December 15th, 2021 and December 16th, 2021 to January 31st, 2022) and relative to the first period (March 8th to May 31st, 2020), the incidence rate ratios (IRRs) of hospitalization were 0.08 (95% CI, 0.03-0.17) and 0.03 (95% CI, 0.01-0.15), respectively. In addition, a relative risk 0.012 CI95% (0.012-0.012) was observed when comparing COVID-19 mortality versus SARS-CoV-2 RNA copies/mL in Boston-area wastewater over the period (16th December 2021 to 30th May 2023) and relative to the first period., Conclusions: The severity of COVID-19 and immunity of our populations evolved over time, resulting in a decrease in case severity. We found the case-hospitalization rate decreased more than 90% in our cohort despite an increase in incidence., (Copyright © 2024 Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. Published by Elsevier España, S.L.U. All rights reserved.)

Objective: This study aimed to evaluate the long-term, symptomatic recovery of healthcare workers from acute COVID-19 infections up to 3 years after the initial COVID-19 outbreak., Methods: A cross-sectional study was performed among employees of a community-based healthcare system in Massachusetts who had a recorded positive COVID-19 test. Survey responses were collected between September 2022 and January 2023. The survey included validated questionnaires: WHOQOL-BREF, EQ-5D-5 L, DASS-21, FCV-19S, K6+, and the Insomnia Severity Index. We compared the long-COVID (ie, symptoms lasting >28 days) and non-long-COVID groups., Results: Among the 280 respondents (15.2% response rate), those with long COVID (73.4%) reported significantly worse quality of life and greater levels of depression, anxiety, and stress metrics. However, no significant difference was found between the two groups' fear of COVID-19., Conclusions: Targeted support for healthcare workers with prolonged symptoms after COVID-19 is warranted., Competing Interests: Lan, Zalaquett, Lutchman, Iliaki, Buley, Nathan, Prieto, and Kales have no relationships/conditions/circumstances that present potential conflict of interest., (Copyright © 2024 American College of Occupational and Environmental Medicine.)

Background: Data on COVID-19 vaccine effectiveness (VE) among healthcare workers (HCWs) during periods of delta variant predominance are limited., Methods: We followed a population of urban Massachusetts HCWs (45% non-White) subject to epidemiologic surveillance. We accounted for covariates such as demographics and community background infection incidence, as well as information bias regarding COVID-19 diagnosis and vaccination status., Results: During the study period (December 16, 2020 to September 30, 2021), 4615 HCWs contributed to a total of 1,152,486 person-days at risk (excluding 309 HCWs with prior infection) and had a COVID-19 incidence rate of 5.2/10,000 (114 infections out of 219,842 person-days) for unvaccinated person-days and 0.6/10,000 (49 infections out of 830,084 person-days) for fully vaccinated person-days, resulting in an adjusted VE of 82.3% (95% CI 75.1-87.4%). For the secondary analysis limited to the period of delta variant predominance in Massachusetts (i.e., July 1 to September 30, 2021), we observed an adjusted VE of 76.5% (95% CI 40.9-90.6%). Independently, we found no re-infection among those with prior COVID-19, contributing to 74,557 re-infection-free person-days, adding to the evidence base for the robustness of naturally acquired immunity., Conclusions: We found a VE of 76.5% against the delta variant. Our work also provides further evidence of naturally acquired immunity., (© 2022. The Author(s).)

Objective: To better understand coronavirus disease 2019 (COVID-19) transmission among healthcare workers (HCWs), we investigated occupational and nonoccupational risk factors associated with cumulative COVID-19 incidence among a Massachusetts HCW cohort., Design, Setting, and Participants: The retrospective cohort study included adult HCWs in a single healthcare system from March 9 to June 3, 2020., Methods: The SARS-CoV-2 nasopharyngeal RT-PCR results and demographics of the study participants were deidentified and extracted from an established occupational health, COVID-19 database at the healthcare system. HCWs from each particular job grouping had been categorized into frontline or nonfrontline workers. Incidence rate ratios (IRRs) and odds ratios (ORs) were used to compare subgroups after excluding HCWs involved in early infection clusters before universal masking began. A sensitivity analysis was performed comparing jobs with the greatest potential occupational risks with others., Results: Of 5,177 HCWs, 152 (2.94%) were diagnosed with COVID-19. Affected HCWs resided in areas with higher community attack rates (median, 1,755.2 vs 1,412.4 cases per 100,000; P < .001; multivariate-adjusted IRR, 1.89; 95% CI, 1.03-3.44 comparing fifth to first quintile of community rates). After multivariate adjustment, African-American and Hispanic HCWs had higher incidence of COVID-19 than non-Hispanic white HCWs (IRR, 2.78; 95% CI, 1.78-4.33; and IRR, 2.41, 95% CI, 1.42-4.07, respectively). After adjusting for race and residential rates, frontline HCWs had a higher IRR (1.73, 95% CI, 1.16-2.54) than nonfrontline HCWs overall, but not within specific job categories nor when comparing the highest risk jobs to others., Conclusions: After universal masking was instituted, the strongest risk factors associated with HCW COVID-19 infection were residential community infection rate and race.

SARS-CoV-2 antibody seroprevalence among health-care workers (HCW) can assess past exposure and possible immunity, which varies across different regions, populations and times. We investigated the seroprevalence among HCW in Massachusetts (a region suffering high COVID-19 mortality) at the end of first wave of the SARS-CoV-2 pandemic. All HCW at Cambridge Health Alliance were invited to participate in this cross-sectional survey in June 2020. Those who volunteered, consented and provided a blood sample were included. Dried blood specimens from finger-prick sampling collected either at home by each HCW or onsite by the study team were analyzed for anti-SARS-CoV-2 IgM and IgG to the virus' receptor binding domain, using an enzyme-linked immunosorbent assay. IgM and IgG antibody abundance were categorized based on the number of standard deviations above the cross-reacting levels found in existing, pre-pandemic blood samples previously obtained by the Ragon Institute and analyzed by the Broad Institute (Cambridge, MA). Seroprevalence estimates were made based on 'positive' IgM or IgG using 'low' (>6 SD), 'medium' (>4.5 SD), and 'high' prevalence cutoffs (>3 SD).A total of 433 out of 5,204 eligible HCWs consented and provided samples. Participating HCWs had a lower cumulative incidence (from the start of the pandemic up to the bloodspot collections) of SARS-CoV-2 RT-PCR positivity (1.85%) compared to non-participants (3.29%). The low, medium, and high seroprevalence estimates were 8.1%, 11.3%, and 14.5%, respectively. The weighted estimates based on past PCR positivity were 13.9%, 19.4%, and 24.9%, respectively, for the entire healthcare system population after accounting for participation bias.

Background: Healthcare workers (HCWs) and other essential workers are at risk of occupational infection during the COVID-19 pandemic. Several infection control strategies have been implemented. Evidence shows that universal masking can mitigate COVID-19 infection, though existing research is limited by secular trend bias., Aims: To investigate the effect of hospital universal masking on COVID-19 incidence among HCWs compared to the general population., Methods: We compared the 7-day average incidence rates between a Massachusetts (USA) healthcare system and Massachusetts residents statewide. The study period was from 17 March (the date of first incident case in the healthcare system) to 6 May (the date Massachusetts implemented public masking). The healthcare system implemented universal masking on 26 March, we allotted a 5-day lag for effect onset and peak COVID-19 incidence in Massachusetts was 20 April. Thus, we categorized 17-31 March as the pre-intervention phase, 1-20 April the intervention phase and 21 April to 6 May the epidemic decline phase. Temporal incidence trends (i.e. 7-day average slopes) were compared using standardized coefficients from linear regression models., Results: The standardized coefficients were similar between the healthcare system and the state in both the pre-intervention and epidemic decline phases. During the intervention phase, the healthcare system's epidemic slope became negative (standardized β: -0.68, 95% CI: -1.06 to -0.31), while Massachusetts' slope remained positive (standardized β: 0.99, 95% CI: 0.94 to 1.05)., Conclusions: Universal masking was associated with a decreasing COVID-19 incidence trend among HCWs, while the infection rate continued to rise in the surrounding community., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Coronavirus 2019 disease (COVID-19) is caused by the virus SARS-CoV-2, transmissible both person-to-person and from contaminated surfaces. Early COVID-19 detection among healthcare workers (HCWs) is crucial for protecting patients and the healthcare workforce. Because of limited testing capacity, symptom-based screening may prioritize testing and increase diagnostic accuracy., Methods and Findings: We performed a retrospective study of HCWs undergoing both COVID-19 telephonic symptom screening and nasopharyngeal SARS-CoV-2 assays during the period, March 9-April 15, 2020. HCWs with negative assays but progressive symptoms were re-tested for SARS-CoV-2. Among 592 HCWs tested, 83 (14%) had an initial positive SARS-CoV-2 assay. Fifty-nine of 61 HCWs (97%) who were asymptomatic or reported only sore throat/nasal congestion had negative SARS-CoV-2 assays (P = 0.006). HCWs reporting three or more symptoms had an increased multivariate-adjusted odds of having positive assays, 1.95 (95% CI: 1.10-3.64), which increased to 2.61 (95% CI: 1.50-4.45) for six or more symptoms. The multivariate-adjusted odds of a positive assay were also increased for HCWs reporting fever and a measured temperature ≥ 37.5°C (3.49 (95% CI: 1.95-6.21)), and those with myalgias (1.83 (95% CI: 1.04-3.23)). Anosmia/ageusia (i.e. loss of smell/loss of taste) was reported less frequently (16%) than other symptoms by HCWs with positive assays, but was associated with more than a seven-fold multivariate-adjusted odds of a positive test: OR = 7.21 (95% CI: 2.95-17.67). Of 509 HCWs with initial negative SARS-CoV-2 assays, nine had symptom progression and positive re-tests, yielding an estimated negative predictive value of 98.2% (95% CI: 96.8-99.0%) for the exclusion of clinically relevant COVID-19., Conclusions: Symptom and temperature reports are useful screening tools for predicting SARS-CoV-2 assay results in HCWs. Anosmia/ageusia, fever, and myalgia were the strongest independent predictors of positive assays. The absence of symptoms or symptoms limited to nasal congestion/sore throat were associated with negative assays., Competing Interests: The authors have declared that no competing interests exist.