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COVID-19 cases in the United States, first reported on January 22, 2020, began to increase in March 2020 (1). The pandemic resulted in a substantial number of employed persons being [...]

Essential and frontline workers experience repeated occupational exposure to SARS-CoV-2 (1). The variant B.1.1.529 (Omicron) is characterized by unprecedented transmissibility and potential for immune evasion, which led to a surge [...]

In response to the then-evolving COVID-19 pandemic, a public health emergency was declared in the United States on January 31, 2020, and several closure and containment policies were subsequently put [...]

Pregnant people face increased risk of severe COVID-19. Current guidelines recommend updated COVID-19 vaccination (2023–2024) for those aged ≥6 months, irrespective of pregnancy status. To refine recommendations for pregnant people, further data are needed. Using a test-negative design, we evaluated COVID-19 vaccine effectiveness against medically attended COVID-19 with COVID-19–like illness among pregnant people aged 18 to 45 years during June 2022 to August 2023. When doses were received during pregnancy, vaccine effectiveness was 52% (95% CI, 29%–67%); when received <6 months prior to pregnancy, 28% (95% CI, 11%–42%); and when received ≥6 months prior to pregnancy, 6% (95% CI, −11% to 21%). Pregnant people should stay up-to-date with recommended COVID-19 vaccination. [ABSTRACT FROM AUTHOR]

Background We assessed associations between binding antibody (bAb) concentration <5 days from symptom onset and testing positive for COVID-19 among patients in a test-negative study. Methods From October 2021 to June 2022, study sites in 7 states enrolled patients aged ≥6 months presenting with acute respiratory illness. Respiratory specimens were tested for SARS-CoV-2. In blood specimens, we measured concentrations of anti-SARS-CoV-2 antibodies against the spike protein receptor binding domain (RBD) and nucleocapsid antigens from the ancestral strain in standardized bAb units (BAU). Percentage change in odds of COVID-19 by increasing anti-RBD bAb was estimated via logistic regression as (1 – adjusted odds ratio of COVID-19) × 100, adjusting for COVID-19 mRNA vaccine doses, age, site, and high-risk exposure. Results Out of 2018 symptomatic patients, 662 (33%) tested positive for acute SARS-CoV-2 infection. Geometric mean RBD bAb levels were lower among COVID-19 cases than SARS-CoV-2 test-negative controls during the Delta-predominant period (112 vs 498 BAU/mL) and Omicron-predominant period (823 vs 1189 BAU/mL). Acute-phase ancestral spike RBD bAb levels associated with 50% lower odds of COVID-19 were 1968 BAU/mL against Delta and 3375 BAU/mL against Omicron; thresholds may differ in other laboratories. Conclusions During acute illness, antibody concentrations against ancestral spike RBD were associated with protection against COVID-19. [ABSTRACT FROM AUTHOR]

Background The 2022–2023 United States influenza season had unusually early influenza activity with high hospitalization rates. Vaccine-matched A(H3N2) viruses predominated, with lower levels of A(H1N1)pdm09 activity also observed. Methods Using the test-negative design, we evaluated influenza vaccine effectiveness (VE) during the 2022–2023 season against influenza A–associated emergency department/urgent care (ED/UC) visits and hospitalizations from October 2022 to March 2023 among adults (aged ≥18 years) with acute respiratory illness (ARI). VE was estimated by comparing odds of seasonal influenza vaccination among case-patients (influenza A test positive by molecular assay) and controls (influenza test negative), applying inverse-propensity-to-be-vaccinated weights. Results The analysis included 85 389 ED/UC ARI encounters (17.0% influenza A positive; 37.8% vaccinated overall) and 19 751 hospitalizations (9.5% influenza A positive; 52.8% vaccinated overall). VE against influenza A–associated ED/UC encounters was 44% (95% confidence interval [CI], 40%–47%) overall and 45% and 41% among adults aged 18–64 and ≥65 years, respectively. VE against influenza A–associated hospitalizations was 35% (95% CI, 27%–43%) overall and 23% and 41% among adults aged 18–64 and ≥65 years, respectively. Conclusions VE was moderate during the 2022–2023 influenza season, a season characterized with increased burden of influenza and co-circulation with other respiratory viruses. Vaccination is likely to substantially reduce morbidity, mortality, and strain on healthcare resources. [ABSTRACT FROM AUTHOR]

Background There are limited data on whether hybrid immunity differs by count and order of immunity-conferring events (infection with severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] or vaccination against coronavirus disease 2019 [COVID-19]). From a multi-site cohort of frontline workers, we examined the heterogeneity of the effect of hybrid immunity on SARS-CoV-2 antibody levels. Methods Exposures included event count and event order, categorized into 7 permutations. Outcome was level of serum antibodies against receptor-binding domain (RBD) of the ancestral SARS-CoV-2 spike protein (total RBD-binding immunoglobulin). Means were examined up to 365 days after each of the first to seventh events. Results Analysis included 5793 participants measured from 7 August 2020 to 15 April 2023. Hybrid immunity from infection before 1 or 2 vaccine doses elicited modestly superior antibody responses after the second and third events (compared with infections or vaccine doses alone). This superiority was not repeated after additional events. Among adults infected before vaccination, adjusted geometric mean ratios (95% confidence interval [CI]) of anti-RBD early response (versus vaccinated only) were 1.23 (1.14–1.33), 1.09 (1.03–1.14), 0.87 (.81–.94), and 0.99 (.85–1.15) after the second to fifth events, respectively. Post-vaccination infections elicited superior responses; adjusted geometric mean ratios (95% CI) of anti-RBD early response (versus vaccinated only) were 0.93 (.75–1.17), 1.11 (1.06–1.16), 1.17 (1.11–1.24), and 1.20 (1.07–1.34) after the second to fifth events, respectively. Conclusions Evidence of heterogeneity in antibody levels by permutations of infection and vaccination history could inform COVID-19 vaccination policy. [ABSTRACT FROM AUTHOR]

We describe humoral immune responses in 105 ambulatory patients with laboratory‐confirmed SARS‐CoV‐2 Omicron variant infection. In dried blood spot (DBS) collected within 5 days of illness onset and during convalescence, we measured binding antibody (bAb) against ancestral spike protein receptor binding domain (RBD) and nucleocapsid (N) protein using a commercial multiplex bead assay. Geometric mean bAb concentrations against RBD increased by a factor of 2.5 from 1258 to 3189 units/mL and by a factor of 47 against N protein from 5.5 to 259 units/mL between acute illness and convalescence; lower concentrations were associated with greater geometric mean ratios. Paired DBS specimens may be used to evaluate humoral response to SARS‐CoV‐2 infection. [ABSTRACT FROM AUTHOR]

Background: The 2022–23 US influenza season peaked early in fall 2022. Methods: Late‐season influenza vaccine effectiveness (VE) against outpatient, laboratory‐confirmed influenza was calculated among participants of the US Influenza VE Network using a test‐negative design. Results: Of 2561 participants enrolled from December 12, 2022 to April 30, 2023, 91 laboratory‐confirmed influenza cases primarily had A(H1N1)pdm09 (6B.1A.5a.2a.1) or A(H3N2) (3C.2a1b.2a.2b). Overall, VE was 30% (95% confidence interval −9%, 54%); low late‐season activity precluded estimation for most subgroups. Conclusions: 2022–23 late‐season outpatient influenza VE was not statistically significant. Genomic characterization may improve the identification of influenza viruses that circulate postinfluenza peak. [ABSTRACT FROM AUTHOR]

The annual economic burden of influenza in the United States, depending on the severity of the influenza season, ranges from $15 billion to $64 billion, of which lost productivity accounts [...]

Background Influenza circulation during the 2022–2023 season in the United States largely returned to pre–coronavirus disease 2019 (COVID-19)-pandemic patterns and levels. Influenza A(H3N2) viruses were detected most frequently this season, predominately clade 3C.2a1b.2a, a close antigenic match to the vaccine strain. Methods To understand effectiveness of the 2022–2023 influenza vaccine against influenza-associated hospitalization, organ failure, and death, a multicenter sentinel surveillance network in the United States prospectively enrolled adults hospitalized with acute respiratory illness between 1 October 2022, and 28 February 2023. Using the test-negative design, vaccine effectiveness (VE) estimates against influenza-associated hospitalization, organ failures, and death were measured by comparing the odds of current-season influenza vaccination in influenza-positive case-patients and influenza-negative, SARS-CoV-2–negative control-patients. Results A total of 3707 patients, including 714 influenza cases (33% vaccinated) and 2993 influenza- and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–negative controls (49% vaccinated) were analyzed. VE against influenza-associated hospitalization was 37% (95% confidence interval [CI]: 27%–46%) and varied by age (18–64 years: 47% [30%–60%]; ≥65 years: 28% [10%–43%]), and virus (A[H3N2]: 29% [6%–46%], A[H1N1]: 47% [23%–64%]). VE against more severe influenza-associated outcomes included: 41% (29%–50%) against influenza with hypoxemia treated with supplemental oxygen; 65% (56%–72%) against influenza with respiratory, cardiovascular, or renal failure treated with organ support; and 66% (40%–81%) against influenza with respiratory failure treated with invasive mechanical ventilation. Conclusions During an early 2022–2023 influenza season with a well-matched influenza vaccine, vaccination was associated with reduced risk of influenza-associated hospitalization and organ failure. [ABSTRACT FROM AUTHOR]

Background During the 2022–2023 influenza season, the United States experienced the highest influenza-associated pediatric hospitalization rate since 2010–2011. Influenza A/H3N2 infections were predominant. Methods We analyzed acute respiratory illness (ARI)–associated emergency department or urgent care (ED/UC) encounters or hospitalizations at 3 health systems among children and adolescents aged 6 months–17 years who had influenza molecular testing during October 2022–March 2023. We estimated influenza A vaccine effectiveness (VE) using a test-negative approach. The odds of vaccination among influenza-A–positive cases and influenza-negative controls were compared after adjusting for confounders and applying inverse-propensity-to-be-vaccinated weights. We developed overall and age-stratified VE models. Results Overall, 13 547 of 44 787 (30.2%) eligible ED/UC encounters and 263 of 1862 (14.1%) hospitalizations were influenza-A–positive cases. Among ED/UC patients, 15.2% of influenza-positive versus 27.1% of influenza-negative patients were vaccinated; VE was 48% (95% confidence interval [CI], 44–52%) overall, 53% (95% CI, 47–58%) among children aged 6 months–4 years, and 38% (95% CI, 30–45%) among those aged 9–17 years. Among hospitalizations, 17.5% of influenza-positive versus 33.4% of influenza-negative patients were vaccinated; VE was 40% (95% CI, 6–61%) overall, 56% (95% CI, 23–75%) among children ages 6 months–4 years, and 46% (95% CI, 2–70%) among those 5–17 years. Conclusions During the 2022–2023 influenza season, vaccination reduced the risk of influenza-associated ED/UC encounters and hospitalizations by almost half (overall VE, 40–48%). Influenza vaccination is a critical tool to prevent moderate-to-severe influenza illness in children and adolescents. [ABSTRACT FROM AUTHOR]

Background: Symptoms of COVID-19 including fatigue and dyspnea, may persist for weeks to months after SARS-CoV-2 infection. This study compared self-reported disability among SARS-CoV-2-positive and negative persons with mild to moderate COVID-19-like illness who presented for outpatient care before widespread COVID-19 vaccination. Methods: Unvaccinated adults with COVID-19-like illness enrolled within 10 days of illness onset at three US Flu Vaccine Effectiveness Network sites were tested for SARS-CoV-2 by molecular assay. Enrollees completed an enrollment questionnaire and two follow-up surveys (7–24 days and 2–7 months after illness onset) online or by phone to assess illness characteristics and health status. The second follow-up survey included questions measuring global health, physical function, fatigue, and dyspnea. Scores in the four domains were compared by participants' SARS-CoV-2 test results in univariate analysis and multivariable Gamma regression. Results: During September 22, 2020 – February 13, 2021, 2712 eligible adults were enrolled, 1541 completed the first follow-up survey, and 650 completed the second follow-up survey. SARS-CoV-2-positive participants were more likely to report fever at acute illness but were otherwise comparable to SARS-CoV-2-negative participants. At first follow-up, SARS-CoV-2-positive participants were less likely to have reported fully or mostly recovered from their illness compared to SARS-CoV-2-negative participants. At second follow-up, no differences by SARS-CoV-2 test results were detected in the four domains in the multivariable model. Conclusion: Self-reported disability was similar among outpatient SARS-CoV-2-positive and -negative adults 2–7 months after illness onset. [ABSTRACT FROM AUTHOR]

Background: Although psychiatric disorders have been associated with reduced immune responses to other vaccines, it remains unknown whether they influence COVID‐19 vaccine effectiveness (VE). This study evaluated risk of COVID‐19 hospitalization and estimated mRNA VE stratified by psychiatric disorder status. Methods: In a retrospective cohort analysis of the VISION Network in four US states, the rate of laboratory‐confirmed COVID‐19‐associated hospitalization between December 2021 and August 2022 was compared across psychiatric diagnoses and by monovalent mRNA COVID‐19 vaccination status using Cox proportional hazards regression. Results: Among 2,436,999 adults, 22.1% had ≥1 psychiatric disorder. The incidence of COVID‐19‐associated hospitalization was higher among patients with any versus no psychiatric disorder (394 vs. 156 per 100,000 person‐years, p < 0.001). Any psychiatric disorder (adjusted hazard ratio [aHR], 1.27; 95% CI, 1.18–1.37) and mood (aHR, 1.25; 95% CI, 1.15–1.36), anxiety (aHR, 1.33, 95% CI, 1.22–1.45), and psychotic (aHR, 1.41; 95% CI, 1.14–1.74) disorders were each significant independent predictors of hospitalization. Among patients with any psychiatric disorder, aHRs for the association between vaccination and hospitalization were 0.35 (95% CI, 0.25–0.49) after a recent second dose, 0.08 (95% CI, 0.06–0.11) after a recent third dose, and 0.33 (95% CI, 0.17–0.66) after a recent fourth dose, compared to unvaccinated patients. Corresponding VE estimates were 65%, 92%, and 67%, respectively, and were similar among patients with no psychiatric disorder (68%, 92%, and 79%). Conclusion: Psychiatric disorders were associated with increased risk of COVID‐19‐associated hospitalization. However, mRNA vaccination provided similar protection regardless of psychiatric disorder status, highlighting its benefit for individuals with psychiatric disorders. [ABSTRACT FROM AUTHOR]

Background The epidemiology of coronavirus disease 2019 (COVID-19) continues to develop with emerging variants, expanding population-level immunity, and advances in clinical care. We describe changes in the clinical epidemiology of COVID-19 hospitalizations and risk factors for critical outcomes over time. Methods We included adults aged ≥18 years from 10 states hospitalized with COVID-19 June 2021–March 2023. We evaluated changes in demographics, clinical characteristics, and critical outcomes (intensive care unit admission and/or death) and evaluated critical outcomes risk factors (risk ratios [RRs]), stratified by COVID-19 vaccination status. Results A total of 60 488 COVID-19–associated hospitalizations were included in the analysis. Among those hospitalized, median age increased from 60 to 75 years, proportion vaccinated increased from 18.2% to 70.1%, and critical outcomes declined from 24.8% to 19.4% (all P <.001) between the Delta (June–December, 2021) and post-BA.4/BA.5 (September 2022–March 2023) periods. Hospitalization events with critical outcomes had a higher proportion of ≥4 categories of medical condition categories assessed (32.8%) compared to all hospitalizations (23.0%). Critical outcome risk factors were similar for unvaccinated and vaccinated populations; presence of ≥4 medical condition categories was most strongly associated with risk of critical outcomes regardless of vaccine status (unvaccinated: adjusted RR, 2.27 [95% confidence interval {CI}, 2.14–2.41]; vaccinated: adjusted RR, 1.73 [95% CI, 1.56–1.92]) across periods. Conclusions The proportion of adults hospitalized with COVID-19 who experienced critical outcomes decreased with time, and median patient age increased with time. Multimorbidity was most strongly associated with critical outcomes. [ABSTRACT FROM AUTHOR]