Overview and Methods for the Youth Risk Behavior Surveillance System - United States, 2021.

The Youth Risk Behavior Surveillance System (YRBSS) is the largest public health surveillance system in the United States, monitoring a broad range of health-related behaviors among high school students. The system includes a nationally representative Youth Risk Behavior Survey (YRBS) and separate school-based YRBSs conducted by states, tribes, territories, and local school districts. In 2021, these surveys were conducted during the COVID-19 pandemic. The pandemic underscored the importance of data in understanding changes in youth risk behaviors and addressing the multifaceted public health needs of youths. This overview report describes 2021 YRBSS survey methodology, including sampling, data collection procedures, response rates, data processing, weighting, and analyses. The 2021 YRBS participation map, survey response rates, and a detailed examination of student demographic characteristics are included in this report. During 2021, in addition to the national YRBS, a total of 78 surveys were administered to high school students across the United States, representing the national population, 45 states, two tribal governments, three territories, and 28 local school districts. YRBSS data from 2021 provided the first opportunity since the onset of the COVID-19 pandemic to compare youth health behaviors using long-term public health surveillance. Approximately half of all student respondents represented racial and ethnic minority groups, and approximately one in four identified as lesbian, gay, bisexual, questioning, or other (a sexual identity other than heterosexual) (LGBQ+). These findings reflect shifts in youth demographics, with increased percentages of racial and ethnic minority and LGBQ+ youths compared with previous YRBSS cycles. Educators, parents, local decision makers, and other partners use YRBSS data to monitor health behavior trends, guide school health programs, and develop local and state policy. These and future data can be used in developing health equity strategies to address long-term disparities so that all youths can thrive in safe and supportive environments. This overview and methods report is one of 11 featured in this MMWR supplement. Each report is based on data collected using methods presented in this overview. A full description of YRBSS results and downloadable data are available (https://www.cdc.gov/healthyyouth/data/yrbs/index.htm).

Urban-rural divide in COVID-19 infection and vaccination rates in healthcare workers in British Columbia, Canada.

Introduction: Healthcare workers (HCWs) play a critical role in responding to the COVID-19 pandemic. Early in the pandemic, urban centres were hit hardest globally; rural areas gradually became more impacted. We compared COVID-19 infection and vaccine uptake in HCWs living in urban versus rural locations within, and between, two health regions in British Columbia (BC), Canada. We also analysed the impact of a vaccine mandate for HCWs. Methods: We tracked laboratory-confirmed SARS-CoV-2 infections, positivity rates and vaccine uptake in all 29,021 HCWs in Interior Health (IH) and all 24,634 HCWs in Vancouver Coastal Health (VCH), by occupation, age and home location, comparing to the general population in that region. We then evaluated the impact of infection rates as well as the mandate on vaccination uptake. Results: While we found an association between vaccine uptake by HCWs and HCW COVID-19 rates in the preceding 2-week period, the higher rates of COVID-19 infection in some occupational groups did not lead to increased vaccination in these groups. By 27 October 2021, the date that unvaccinated HCWs were prohibited from providing healthcare, only 1.6% in VCH compared with 6.5% in IH remained unvaccinated. Rural workers in both areas had significantly higher unvaccinated rates compared with urban dwellers. Over 1800 workers, comprising 6.7% of rural HCWs and 3.6% of urban HCWs, remained unvaccinated and set to be terminated from their employment. While the mandate prompted a significant increase in uptake of second doses, the impact on the unvaccinated was less clear. Conclusions: As rural areas often suffer from under-staffing, loss of HCWs could have serious impacts on healthcare provision as well as on the livelihoods of unvaccinated HCWs. Greater efforts are needed to understand how to better address the drivers of rural-related vaccine hesitancy.

Résumé Introduction: Les travailleurs de la santé (TS) jouent un rôle essentiel dans la réponse à la pandémie de COVID-19. Au début de la pandémie, les centres urbains ont été les plus durement touchés à l'échelle mondiale; les zones rurales ont progressivement été plus touchées. Nous avons comparé l'infection à la COVID-19 et l'adoption du vaccin chez les travailleuses et travailleurs de la santé vivant dans des zones urbaines et rurales au sein de deux régions sanitaires de la Colombie-Britannique (C.-B.), au Canada, et entre ces régions. Nous avons également analysé l'impact d'un mandat de vaccination pour les travailleuses et travailleurs de la santé. Méthodes: Nous avons suivi les infections au SRAS-CoV-2 confirmées en laboratoire, les taux de positivité et l'adoption du vaccin chez les 29 021 TS d'Interior Health (IH) et les 24 634 TS de Vancouver Coastal Health (VCH), par profession, âge et lieu de résidence, en les comparant à la population générale de cette région. Nous avons ensuite évalué l'impact des taux d'infection ainsi que du mandat sur le recours à la vaccination. Résultats: Bien que nous ayons trouvé une association entre l'adoption du vaccin par les TS et les taux de COVID-19 des travailleurs de la santé au cours de la période de deux semaines précédentes, les taux plus élevés d'infection par la COVID-19 dans certains groupes professionnels n'ont pas entraîné une augmentation de la vaccination dans ces groupes. En date du 27 octobre 2021, date à laquelle il était interdit aux travailleuses et travailleurs de santé non vaccinés de fournir des soins de santé, seul 1,6% des travailleuses et travailleurs de la VCH, contre 6,5% des travailleuses et travailleurs de l'IH, n'étaient toujours pas vaccinés. Les travailleuses et travailleurs ruraux des deux zones présentaient des taux de non-vaccination significativement plus élevés que les citadins. Plus de 1 800 travailleuses et travailleurs, soit 6,7% des TS ruraux et 3,6% des TS urbains, n'étaient toujours pas vaccinés et devaient être licenciés. Bien que le mandat ait entraîné une augmentation significative de la prise des deuxièmes doses, l'impact sur les personnes non-vaccinées était moins clair. Conclusions: Comme les zones rurales souffrent souvent d'un manque de personnel, la perte de TS pourrait avoir de graves répercussions sur la prestation des soins de santé ainsi que sur les moyens de subsistance des TS non-vaccinés. Des efforts plus importants sont nécessaires pour comprendre comment mieux aborder les facteurs d'hésitation à SE faire vacciner en milieu rural. Mots-clés: Travailleuses et travailleurs de la santé, COVID-19, vaccination, mandat de vaccination, milieu rural.

COVID-19 hospitalisations in immunocompromised individuals in the Omicron era: a population-based observational study using surveillance data in British Columbia, Canada.

Background: People with immune dysfunction are at higher risk of severe outcomes from COVID-19 infection, but relatively little epidemiologic information is available for mostly vaccinated population in the Omicron era. This population-based study compared relative risk of breakthrough COVID-19 hospitalisation among vaccinated people identified as clinically extremely vulnerable (CEV) vs non-CEV individuals before treatment became more widely available. Methods: COVID-19 cases and hospitalisations reported to the British Columbia Centre for Disease Control (BCCDC) between January 7, 2022 and March 14, 2022 were linked with data on their vaccination and CEV status. Case hospitalisation rates were estimated across CEV status, age groups and vaccination status. For vaccinated individuals, risk ratios for breakthrough hospitalisations were calculated for CEV and non-CEV populations matched on sex, age group, region, and vaccination characteristics. Findings: Among CEV individuals, a total of 5591 COVID-19 reported cases were included, among which 1153 were hospitalized. A third vaccine dose with mRNA vaccine offered additional protection against severe illness in both CEV and non-CEV individuals. However, 2- and 3-dose vaccinated CEV population still had a significantly higher relative risk of breakthrough COVID-19 hospitalisation compared with non-CEV individuals. Interpretation: Vaccinated CEV population remains a higher risk group in the context of circulating Omicron variant and may benefit from additional booster doses and pharmacotherapy. Funding: BC Centre for Disease Control and Provincial Health Services Authority.

Abbott ID NOW™ COVID-19 assay: do not discard the swab.

We compared the performance of ID NOW™ COVID-19 assay nasal swabs with RT-PCR of nasopharyngeal swabs for SARS-CoV-2 in an outbreak setting, determining whether addition of RT-PCR of residual nasal swabs (rNS) (post ID NOW™ elution) would increase overall analytic sensitivity. Devices were placed at 2 long term and 1 acute care sites and 51 participants were recruited. Prospective paired nasopharyngeal and nasal samples were collected for RT-PCR and ID NOW™.  ID NOW™ had a positive and negative categorical agreement of 86% and 93% compared to RT-PCR of nasopharyngeal swabs. Sensitivity and specificity of the ID NOW™ was 86% and 100%, positive and negative predictive value was 100% and 95% (COVID-19 positivity rate: 8%). Addition of rNS RT-PCR increased the positive and negative categorical agreement to 93% and 97%. Based on these results, we propose an alternative workflow which includes complementary testing of rNS on a secondary assay.

Masking strategy to protect healthcare workers from COVID-19: An umbrella meta-analysis.

BACKGROUND: The burden of severe disease and death due to SARS-CoV-2 (COVID-19) pandemic among healthcare workers (HCWs) worldwide has been substantial. Masking is a critical control measure to effectively protect HCWs from respiratory infectious diseases, yet for COVID-19, masking policies have varied considerably across jurisdictions. As Omicron variants began to be predominant, the value of switching from a permissive approach based on a point of care risk assessment (PCRA) to a rigid masking policy needed to be assessed. METHODS: A literature search was conducted in MEDLINE (Ovid platform), Cochrane Library, Web of Science (Ovid platform), and PubMed to June 2022. An umbrella review of meta-analyses investigating protective effects of N95 or equivalent respirators and medical masks was then conducted. Data extraction, evidence synthesis and appraisal were duplicated. RESULTS: While the results of Forest plots slightly favoured N95 or equivalent respirators over medical masks, eight of the ten meta-analyses included in the umbrella review were appraised as having very low certainty and the other two as having low certainty. CONCLUSION: The literature appraisal, in conjunction with risk assessment of the Omicron variant, side-effects and acceptability to HCWs, along with the precautionary principle, supported maintaining the current policy guided by PCRA rather than adopting a more rigid approach. Well-designed prospective multi-centre trials, with systematic attention to the diversity of healthcare settings, risk levels and equity concerns are needed to support future masking policies.

Cost-effectiveness of remdesivir plus usual care versus usual care alone for hospitalized patients with COVID-19: an economic evaluation as part of the Canadian Treatments for COVID-19 (CATCO) randomized clinical trial.

BACKGROUND: The role of remdesivir in the treatment of hospitalized patients with COVID-19 remains ill-defined. We conducted a cost-effectiveness analysis alongside the Canadian Treatments for COVID-19 (CATCO) open-label, randomized clinical trial evaluating remdesivir. METHODS: Patients with COVID-19 in Canadian hospitals from Aug. 14, 2020, to Apr. 1, 2021, were randomly assigned to receive remdesivir plus usual care versus usual care alone. Taking a public health care payer's perspective, we collected in-hospital outcomes and health care resource utilization alongside estimated unit costs in 2020 Canadian dollars over a time horizon from randomization to hospital discharge or death. Data from 1281 adults admitted to 52 hospitals in 6 Canadian provinces were analyzed. RESULTS: The total mean cost per patient was $37 918 (standard deviation [SD] $42 413; 95% confidence interval [CI] $34 617 to $41 220) for patients randomly assigned to the remdesivir group and $38 026 (SD $46 021; 95% CI $34 480 to $41 573) for patients receiving usual care (incremental cost -$108 [95% CI -$4953 to $4737], p > 0.9). The difference in proportions of in-hospital deaths between remdesivir and usual care groups was -3.9% (18.7% v. 22.6%, 95% CI -8.3% to 1.0%, p = 0.09). The difference in proportions of incident invasive mechanical ventilation events between groups was -7.0% (8.0% v. 15.0%, 95% CI -10.6% to -3.4%, p = 0.006), whereas the difference in proportions of total mechanical ventilation events between groups was -5.7% (16.4% v. 22.1%, 95% CI -10.0% to -1.4%, p = 0.01). Remdesivir was the dominant intervention (but only marginally less costly, with mildly lower mortality) with an incalculable incremental cost effectiveness ratio; we report results of incremental costs and incremental effects separately. For willingness-to-pay thresholds of $0, $20 000, $50 000 and $100 000 per death averted, a strategy using remdesivir was cost-effective in 60%, 67%, 74% and 79% of simulations, respectively. The remdesivir costs were the fifth highest cost driver, offset by shorter lengths of stay and less mechanical ventilation. INTERPRETATION: From a health care payer perspective, treating patients hospitalized with COVID-19 with remdesivir and usual care appears to be preferrable to treating with usual care alone, albeit with marginal incremental cost and small clinical effects. The added cost of remdesivir was offset by shorter lengths of stay in the intensive care unit and less need for ventilation. STUDY REGISTRATION: ClinicalTrials. gov, no. NCT04330690.

A Mixed-Methods Study of Risk Factors and Experiences of Health Care Workers Tested for the Novel Coronavirus in Canada.

OBJECTIVE: The aims of this study were to investigate occupational and non-work-related risk factors of coronavirus disease 2019 among health care workers (HCWs) in Vancouver Coastal Health, British Columbia, Canada, and to examine how HCWs described their experiences. METHODS: This was a matched case-control study using data from online and phone questionnaires with optional open-ended questions completed by HCWs who sought severe acute respiratory syndrome coronavirus 2 testing between March 2020 and March 2021. Conditional logistic regression and thematic analysis were utilized. RESULTS: Providing direct care to coronavirus disease 2019 patients during the intermediate cohort period (adjusted odds ratio, 1.90; 95% confidence interval, 1.04 to 3.46) and community exposure to a known case in the late cohort period (adjusted odds ratio, 3.595%; confidence interval, 1.86 to 6.83) were associated with higher infection odds. Suboptimal communication, mental stress, and situations perceived as unsafe were common sources of dissatisfaction. CONCLUSIONS: Varying levels of risk between occupational groups call for wider targeting of infection prevention measures. Strategies for mitigating community exposure and supporting HCW resilience are required.

Sensitivity and Diagnostic Yield of the First SARS-CoV-2 Nucleic Acid Amplification Test Performed for Patients Presenting to the Hospital.

Importance: Early and accurate diagnostic testing for SARS-CoV-2 is essential to initiate appropriate treatment and infection control and prevention measures among patients presenting to the hospital. Objective: To evaluate the diagnostic sensitivity of the SARS-CoV-2 nucleic acid amplification test (NAAT) performed within 24 hours of arrival to the emergency department among a nationally representative sample of patients. Design, Setting, and Participants: This diagnostic study was conducted at 47 hospitals across 7 provinces in Canada participating in the Canadian COVID-19 Rapid Response Emergency Department Network among consecutive eligible patients presenting to a participating emergency department who were tested for SARS-CoV-2 from March 1, 2020, to December 31, 2021. Patients not tested within 24 hours of arrival and those presenting with a positive result from a test performed in the community were excluded. Main Outcomes and Measures: The primary outcome was a positive result from the SARS-CoV-2 NAAT. Outcome measures were the diagnostic sensitivity and yield of the SARS-CoV-2 NAAT. Results: Of 132 760 eligible patients (66 433 women [50.0%]; median age, 57 years [IQR, 37-74 years]), 17 174 (12.9%) tested positive for SARS-CoV-2 within 14 days of their first NAAT. The diagnostic sensitivity of the SARS-CoV-2 NAAT was 96.2% (17 070 of 17 740 [95% CI, 95.9%-96.4%]) among all of the tests performed. Estimates ranged from a high of 97.7% (1710 of 1751 [95% CI, 96.8%-98.3%]) on day 2 of symptoms to a low of 90.4% (170 of 188 [95% CI, 85.3%-94.2%]) on day 11 of symptoms among patients presenting with COVID-19 symptoms. Among patients reporting COVID-19 symptoms, the sensitivity of the SARS-CoV-2 NAAT was 97.1% (11 870 of 12 225 [95% CI, 96.7%-97.3%]) compared with 87.6% (812 of 927 [95% CI, 85.2%-89.6%]) among patients without COVID-19 symptoms. The diagnostic yield of the SARS-CoV-2 NAAT was 12.0% (18 985 of 158 004 [95% CI, 11.8%-12.2%]) and varied from a high of 20.0% (445 of 2229 [95% CI, 18.3%-21.6%]) among patients tested on day 10 after symptom onset to a low of 8.1% (1686 of 20 719 [95% CI, 7.7%-8.5%]) among patients presenting within the first 24 hours of symptom onset. Conclusions and Relevance: This study suggests that the diagnostic sensitivity was high for the first SARS-CoV-2 NAAT performed in the hospital and did not vary significantly by symptom duration. Repeated testing of patients with negative test results should be avoided unless their pretest probability of disease is high.

Overview and Methodology of the Adolescent Behaviors and Experiences Survey - United States, January-June 2021.

Many U.S. schools closed nationwide in March 2020 to prevent the spread of COVID-19. School closures and online-only instruction have negatively affected certain students, with studies showing adverse effects of the pandemic on mental health. However, little is known about other experiences such as economic and food insecurity and abuse by a parent, as well as risk behaviors such as alcohol and drug use among youths across the United States during the pandemic. To address this gap, CDC developed the one-time, online Adolescent Behaviors and Experiences Survey (ABES), which was conducted during January-June 2021 to assess student behaviors and experiences during the COVID-19 pandemic among high school students, including unintentional injury, violence, tobacco product use, sexual behaviors, and dietary behaviors. This overview report of the ABES MMWR Supplement describes the ABES methodology, including the student questionnaire and administration, sampling, data collection, weighting, and analysis. ABES used a stratified, three-stage cluster probability-based sampling approach to obtain a nationally representative sample of students in grades 9-12 attending public and private schools. Teachers of selected classes provided students with access to the anonymous online survey while following local consent procedures. Data were collected using a 110-item questionnaire during January-June 2021 in 128 schools. A total of 7,998 students submitted surveys, and 7,705 of these surveys had valid data (i.e., ≥20 questions answered). The school response rate was 38%, the student response rate was 48%, and the overall response rate was 18%. Information on mode of instruction and school-provided equipment was also collected from all sampled schools. This overview report provides student- and school-level characteristics obtained from descriptive analyses, and the other reports in the ABES MMWR Supplement include information on substance use, mental health and suicidality, perceived racism, and disruptions to student life among high school students. Findings from ABES during the COVID-19 pandemic can help guide parents, teachers, school administrators, community leaders, clinicians, and public health officials in decision-making for student support and school health programs.

Remdesivir for the treatment of patients in hospital with COVID-19 in Canada: a randomized controlled trial.

BACKGROUND: The role of remdesivir in the treatment of patients in hospital with COVID-19 remains ill defined in a global context. The World Health Organization Solidarity randomized controlled trial (RCT) evaluated remdesivir in patients across many countries, with Canada enrolling patients using an expanded data collection format in the Canadian Treatments for COVID-19 (CATCO) trial. We report on the Canadian findings, with additional demographics, characteristics and clinical outcomes, to explore the potential for differential effects across different health care systems. METHODS: We performed an open-label, pragmatic RCT in Canadian hospitals, in conjunction with the Solidarity trial. We randomized patients to 10 days of remdesivir (200 mg intravenously [IV] on day 0, followed by 100 mg IV daily), plus standard care, or standard care alone. The primary outcome was in-hospital mortality. Secondary outcomes included changes in clinical severity, oxygen- and ventilator-free days (at 28 d), incidence of new oxygen or mechanical ventilation use, duration of hospital stay, and adverse event rates. We performed a priori subgroup analyses according to duration of symptoms before enrolment, age, sex and severity of symptoms on presentation. RESULTS: Across 52 Canadian hospitals, we randomized 1282 patients between Aug. 14, 2020, and Apr. 1, 2021, to remdesivir (n = 634) or standard of care (n = 648). Of these, 15 withdrew consent or were still in hospital, for a total sample of 1267 patients. Among patients assigned to receive remdesivir, in-hospital mortality was 18.7%, compared with 22.6% in the standard-of-care arm (relative risk [RR] 0.83 (95% confidence interval [CI] 0.67 to 1.03), and 60-day mortality was 24.8% and 28.2%, respectively (95% CI 0.72 to 1.07). For patients not mechanically ventilated at baseline, the need for mechanical ventilation was 8.0% in those assigned remdesivir, and 15.0% in those receiving standard of care (RR 0.53, 95% CI 0.38 to 0.75). Mean oxygen-free and ventilator-free days at day 28 were 15.9 (± standard deviation [SD] 10.5) and 21.4 (± SD 11.3) in those receiving remdesivir and 14.2 (± SD 11) and 19.5 (± SD 12.3) in those receiving standard of care (p = 0.006 and 0.007, respectively). There was no difference in safety events of new dialysis, change in creatinine, or new hepatic dysfunction between the 2 groups. INTERPRETATION: Remdesivir, when compared with standard of care, has a modest but significant effect on outcomes important to patients and health systems, such as the need for mechanical ventilation. Trial registration: ClinicalTrials.gov, no. NCT04330690.

Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools - Georgia, November 16-December 11, 2020.

To meet the educational, physical, social, and emotional needs of children, many U.S. schools opened for in-person learning during fall 2020 by implementing strategies to prevent transmission of SARS-CoV-2, the virus that causes COVID-19 (1,2). To date, there have been no U.S. studies comparing COVID-19 incidence in schools that varied in implementing recommended prevention strategies, including mask requirements and ventilation improvements* (2). Using data from Georgia kindergarten through grade 5 (K-5) schools that opened for in-person learning during fall 2020, CDC and the Georgia Department of Public Health (GDPH) assessed the impact of school-level prevention strategies on incidence of COVID-19 among students and staff members before the availability of COVID-19 vaccines.† Among 169 K-5 schools that participated in a survey on prevention strategies and reported COVID-19 cases during November 16-December 11, 2020, COVID-19 incidence was 3.08 cases among students and staff members per 500 enrolled students.§ Adjusting for county-level incidence, COVID-19 incidence was 37% lower in schools that required teachers and staff members to use masks, and 39% lower in schools that improved ventilation, compared with schools that did not use these prevention strategies. Ventilation strategies associated with lower school incidence included methods to dilute airborne particles alone by opening windows, opening doors, or using fans (35% lower incidence), or in combination with methods to filter airborne particles with high-efficiency particulate absorbing (HEPA) filtration with or without purification with ultraviolet germicidal irradiation (UVGI) (48% lower incidence). Multiple strategies should be implemented to prevent transmission of SARS-CoV-2 in schools (2); mask requirements for teachers and staff members and improved ventilation are important strategies that elementary schools could implement as part of a multicomponent approach to provide safer, in-person learning environments. Universal and correct mask use is still recommended by CDC for adults and children in schools regardless of vaccination status (2).

Simulating drug concentrations in PDMS microfluidic organ chips.

Microfluidic organ-on-a-chip (Organ Chip) cell culture devices are often fabricated using polydimethylsiloxane (PDMS) because it is biocompatible, transparent, elastomeric, and oxygen permeable; however, hydrophobic small molecules can absorb to PDMS, which makes it challenging to predict drug responses. Here, we describe a combined simulation and experimental approach to predict the spatial and temporal concentration profile of a drug under continuous dosing in a PDMS Organ Chip containing two parallel channels separated by a porous membrane that is lined with cultured cells, without prior knowledge of its log P value. First, a three-dimensional finite element model of drug loss into the chip was developed that incorporates absorption, adsorption, convection, and diffusion, which simulates changes in drug levels over time and space as a function of potential PDMS diffusion coefficients and log P values. By then experimentally measuring the diffusivity of the compound in PDMS and determining its partition coefficient through mass spectrometric analysis of the drug concentration in the channel outflow, it is possible to estimate the effective log P range of the compound. The diffusion and partition coefficients were experimentally derived for the antimalarial drug and potential SARS-CoV-2 therapeutic, amodiaquine, and incorporated into the model to quantitatively estimate the drug-specific concentration profile over time measured in human lung airway chips lined with bronchial epithelium interfaced with pulmonary microvascular endothelium. The same strategy can be applied to any device geometry, surface treatment, or in vitro microfluidic model to simulate the spatial and temporal gradient of a drug in 3D without prior knowledge of the partition coefficient or the rate of diffusion in PDMS. Thus, this approach may expand the use of PDMS Organ Chip devices for various forms of drug testing.

Infection control, occupational and public health measures including mRNA-based vaccination against SARS-CoV-2 infections to protect healthcare workers from variants of concern: A 14-month observational study using surveillance data.

BACKGROUND: We evaluated measures to protect healthcare workers (HCWs) in Vancouver, Canada, where variants of concern (VOC) went from <1% VOC in February 2021 to >92% in mid-May. Canada has amongst the longest periods between vaccine doses worldwide, despite Vancouver having the highest P.1 variant rate outside Brazil. METHODS: With surveillance data since the pandemic began, we tracked laboratory-confirmed SARS-CoV-2 infections, positivity rates, and vaccine uptake in all 25,558 HCWs in Vancouver Coastal Health, by occupation and subsector, and compared to the general population. Cox regression modelling adjusted for age and calendar-time calculated vaccine effectiveness (VE) against SARS-CoV-2 in fully vaccinated (≥ 7 days post-second dose), partially vaccinated infection (after 14 days) and unvaccinated HCWs; we also compared with unvaccinated community members of the same age-range. FINDINGS: Only 3.3% of our HCWs became infected, mirroring community rates, with peak positivity of 9.1%, compared to 11.8% in the community. As vaccine coverage increased, SARS-CoV-2 infections declined significantly in HCWs, despite a surge with predominantly VOC; unvaccinated HCWs had an infection rate of 1.3/10,000 person-days compared to 0.89 for HCWs post first dose, and 0.30 for fully vaccinated HCWs. VE compared to unvaccinated HCWs was 37.2% (95% CI: 16.6-52.7%) 14 days post-first dose, 79.2% (CI: 64.6-87.8%) 7 days post-second dose; one dose provided significant protection against infection until at least day 42. Compared with community infection rates, VE after one dose was 54.7% (CI: 44.8-62.9%); and 84.8% (CI: 75.2-90.7%) when fully vaccinated. INTERPRETATION: Rigorous droplet-contact precautions with N95s for aerosol-generating procedures are effective in preventing occupational infection in HCWs, with one dose of mRNA vaccination further reducing infection risk despite VOC and transmissibility concerns. Delaying second doses to allow more widespread vaccination against severe disease, with strict public health, occupational health and infection control measures, has been effective in protecting the healthcare workforce.

Impact of the COVID-19 nonpharmaceutical interventions on influenza and other respiratory viral infections in New Zealand.

Stringent nonpharmaceutical interventions (NPIs) such as lockdowns and border closures are not currently recommended for pandemic influenza control. New Zealand used these NPIs to eliminate coronavirus disease 2019 during its first wave. Using multiple surveillance systems, we observed a parallel and unprecedented reduction of influenza and other respiratory viral infections in 2020. This finding supports the use of these NPIs for controlling pandemic influenza and other severe respiratory viral threats.