SARS-CoV-2 transmission with and without mask wearing or air cleaners in schools in Switzerland: A modeling study of epidemiological, environmental, and molecular data.

BACKGROUND: Growing evidence suggests an important contribution of airborne transmission to the overall spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), in particular via smaller particles called aerosols. However, the contribution of school children to SARS-CoV-2 transmission remains uncertain. The aim of this study was to assess transmission of airborne respiratory infections and the association with infection control measures in schools using a multiple-measurement approach. METHODS AND FINDINGS: We collected epidemiological (cases of Coronavirus Disease 2019 (COVID-19)), environmental (CO2, aerosol and particle concentrations), and molecular data (bioaerosol and saliva samples) over 7 weeks from January to March 2022 (Omicron wave) in 2 secondary schools (n = 90, average 18 students/classroom) in Switzerland. We analyzed changes in environmental and molecular characteristics between different study conditions (no intervention, mask wearing, air cleaners). Analyses of environmental changes were adjusted for different ventilation, the number of students in class, school and weekday effects. We modeled disease transmission using a semi-mechanistic Bayesian hierarchical model, adjusting for absent students and community transmission. Molecular analysis of saliva (21/262 positive) and airborne samples (10/130) detected SARS-CoV-2 throughout the study (weekly average viral concentration 0.6 copies/L) and occasionally other respiratory viruses. Overall daily average CO2 levels were 1,064 ± 232 ppm (± standard deviation). Daily average aerosol number concentrations without interventions were 177 ± 109 1/cm3 and decreased by 69% (95% CrI 42% to 86%) with mask mandates and 39% (95% CrI 4% to 69%) with air cleaners. Compared to no intervention, the transmission risk was lower with mask mandates (adjusted odds ratio 0.19, 95% CrI 0.09 to 0.38) and comparable with air cleaners (1.00, 95% CrI 0.15 to 6.51). Study limitations include possible confounding by period as the number of susceptible students declined over time. Furthermore, airborne detection of pathogens document exposure but not necessarily transmission. CONCLUSIONS: Molecular detection of airborne and human SARS-CoV-2 indicated sustained transmission in schools. Mask mandates were associated with greater reductions in aerosol concentrations than air cleaners and with lower transmission. Our multiple-measurement approach could be used to continuously monitor transmission risk of respiratory infections and the effectiveness of infection control measures in schools and other congregate settings.

Population-based SARS-CoV-2 whole genome sequencing and contact tracing during the COVID-19 pandemic in Switzerland.

BACKGROUND: Testing and contact tracing (CT) can interrupt transmission chains SARS-CoV-2. Whole genome sequencing (WGS) can potentially strengthen these investigations and provide insights on transmission. METHODS: We included all laboratory-confirmed COVID-19 cases diagnosed between June 4 to July 26, 2021, in a Swiss canton. We defined CT clusters based on epidemiological links reported in the CT data and genomic clusters as sequences with no single nucleotide polymorphism (SNP) differences between any two pairs of sequences being compared. We assessed the agreement between CT clusters and genomic clusters. RESULTS: Of 359 COVID-19 cases, 213 were sequenced. Overall, agreement between CT and genomic clusters was low (Kappa coefficient=0.13). Out of 24 CT clusters with at least two sequenced samples, 9 (37.5%) were also linked based on genomic sequencing but in four of these, WGS found additional cases in other CT clusters. Household was most often reported source of infection (101, 28.1%) and home addresses coincided well with CT clusters: In 44 out of 54 CT clusters containing at least two cases (81.5%), all cases of the cluster had the same home address. However, only a quarter of household transmission was confirmed by WGS (6 out of 26 genomic clusters, 23.1%). A sensitivity analysis using ≤1 SNP differences to define genomic clusters resulted in similar results. CONCLUSIONS: WGS data supplemented epidemiological CT data, supported the detection of potential additional clusters missed by CT, and identified misclassified transmissions and sources of infection. Household transmission was overestimated by CT.

Transmission risk of SARS-CoV-2 to healthcare workers -observational results of a primary care hospital contact tracing.

BACKGROUND: The coronavirus disease (COVID)-19 epidemic is evolving rapidly. Healthcare workers are at increased risk for infection, and specific requirements for their protection are advisable to ensure the functioning of the basic healthcare system, including the availability of general practitioners (GPs). Understanding the transmission risk is particularly important for guiding evidence-based protective measures in the primary healthcare setting. METHODS: Healthcare worker contacts of an initially undiagnosed COVID-19 case, who were without personal protective equipment, in particular not wearing facemasks, were screened with nasopharyngeal swabs and polymerase chain reaction tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), irrespective of respiratory symptoms or fever seven days after initial contact. The details of exposure to the index case were obtained during routine contact investigation after unintentional pathogen exposure. RESULTS: Twenty-one healthcare workers reported contacts with the index case. Three healthcare workers reported respiratory symptoms (cough) or low-grade fever within 4 days. None of them tested positive for SARS-CoV-2 at the time of symptom onset. All 21 healthcare workers tested SARS-CoV-2 negative 7 days after initial index case contact, including the three healthcare workers with previous symptoms. Ten of the 21 healthcare workers reported a cumulative exposure time of >15 minutes. Longer cumulative contact times were associated with more individual contacts, reduced contact time per contact and activities with physical patient contact. The closest relative of the index patient tested SARS-CoV-2 positive 2 days after the index case presented at the hospital emergency department. CONCLUSION: We found a low risk of SARS-CoV-2 transmission in a primary care setting. These findings are compatible with previous reports of the highest transmission probability in household settings with prolonged close contacts. The current protective measures for healthcare workers, including strict adherence to basic standard hygiene and facemasks, offer considerable protection during short periods of contact with symptomatic COVID-19 cases by diminishing the risk of direct and indirect transmission.

Impact of the COVID-19 pandemic on TB services at ART programmes in low- and middle-income countries: a multi-cohort survey.

INTRODUCTION: COVID-19 stretched healthcare systems to their limits, particularly in settings with a pre-existing high burden of infectious diseases, including HIV and tuberculosis (TB). We studied the impact of COVID-19 on TB services at antiretroviral therapy (ART) clinics in low- and middle-income countries. METHODS: We surveyed ART clinics providing TB services in the International Epidemiology Databases to Evaluate AIDS (IeDEA) consortium in Africa and the Asia-Pacific until July 2021 (TB diagnoses until the end of 2021). We collected site-level data using standardized questionnaires. RESULTS: Of 46 participating ART clinics, 32 (70%) were in Africa and 14 (30%) in the Asia-Pacific; 52% provided tertiary care. Most clinics (85%) reported disrupted routine HIV care services during the pandemic, both in Africa (84%) and the Asia-Pacific (86%). The most frequently reported impacts were on staff (52%) and resource shortages (37%; protective clothing, face masks and disinfectants). Restrictions in TB health services were observed in 12 clinics (26%), mainly reduced access to TB diagnosis and postponed follow-up visits (6/12, 50% each), and restrictions in TB laboratory services (22%). Restrictions of TB services were addressed by dispensing TB drugs for longer periods than usual (7/12, 58%), providing telehealth services (3/12, 25%) and with changes in directly observed therapy (DOT) (e.g. virtual DOT, 3/12). The number of TB diagnoses at participating clinics decreased by 21% in 2020 compared to 2019; the decline was more pronounced in tertiary than primary/secondary clinics (24% vs. 12%) and in sites from the Asia-Pacific compared to Africa (46% vs. 14%). In 2021, TB diagnoses continued to decline in Africa (-8%) but not in the Asia-Pacific (+62%) compared to 2020. During the pandemic, new infection control measures were introduced or intensified at the clinics, including wearing face masks, hand sanitation and patient triage. CONCLUSIONS: The COVID-19 pandemic led to staff shortages, reduced access to TB care and delays in follow-up visits for people with TB across IeDEA sites in Africa and the Asia-Pacific. Increased efforts are needed to restore and secure ongoing access to essential TB services in these contexts.

Alpha variant coronavirus outbreak in a nursing home despite high vaccination coverage: molecular, epidemiological and immunological studies.

BACKGROUND: Vaccination may control the COVID-19 pandemic, including in nursing homes where many high-risk people live. We conducted extensive outbreak investigations. METHODS: We studied an outbreak at a nursing home in Switzerland where vaccination uptake of mRNA vaccines against SARS-CoV-2 was 82% among residents as of Jan 21/2021. After a vaccinated symptomatic HCW was diagnosed with COVID-19 on Feb 22, we did an outbreak investigations in house A (47 residents, 37 HCWs) using SARS-CoV-2-specific PCR in nasopharyngeal swabs. We performed whole-genome sequencing of SARS-CoV-2 and serological analyses. RESULTS: We identified 17 individuals with positive PCR tests; ten residents (five vaccinated) and seven HCWs (three vaccinated). Median age among residents was 86 years (interquartile range [IQR] 70-90) and 49 years (IQR 29-59) among HCWs. Among the five vaccinated residents, 60% had mild disease and had 40% no symptoms, whereas all five unvaccinated residents had mild to severe disease and two died. The vaccine effectiveness for the prevention of infection among the residents was 73.0% (95% Cl 24.7-90.1). The 12 available genomes were all alpha variants. Neutralizing titers were significantly higher in vaccinated individuals upon re-exposure (>1 week after diagnosis) than in vaccinated, unexposed HCWs (p=0.012). Transmission networks indicated four likely or possible transmissions from vaccinated to other individuals, and 12 transmission events from unvaccinated individuals. CONCLUSIONS: COVID-19 outbreaks can occur in nursing homes, including transmission from vaccinated persons to others. Outbreaks might occur silently, underlining the need for continued testing and basic infection control measures in these high-risk settings.

Vaccination willingness for COVID-19 among healthcare workers: a cross-sectional survey in a Swiss canton.

AIMS OF THE STUDY: Vaccination is regarded as the most promising response to the COVID-19 pandemic. We assessed opinions about COVID-19 vaccination, willingness to be vaccinated, and reasons for vaccination hesitancy among healthcare workers. METHODS: We conducted a cross-sectional, web-based survey among 3,793 healthcare workers in December 2020 in the Canton of Solothurn, Switzerland, before the start of the national COVID-19 vaccination campaign. RESULTS: Median age was 43 years (interquartile range [IQR] 31-53), 2,841 were female (74.9%). A total of 1,511 healthcare workers (39.8%) reported willingness to accept vaccination, whereas 1,114 (29.4%) were unsure and 1,168 (30.8%) would decline vaccination. Among medical doctors, 76.1% were willing, whereas only 27.8% of nurses expressed willingness. Among the 1,168 healthcare workers who would decline vaccination, 1,073 (91.9%) expressed concerns about vaccine safety and side effects. The willingness of healthcare workers to be vaccinated was associated with older age (adjusted odds ratio [aOR] 1.97, 95% confidence interval [Cl] 1.71-2.27) and having been vaccinated for influenza this year (aOR 2.70, 95% Cl 2.20-3.31). Healthcare workers who reported a lack of confidence in government were less likely to be willing to be vaccinated (aOR 0.58, 95% Cl 0.40-0.84), and women were less willing to be vaccinated than men (OR 0.33, 95% CI 0.28-0.38). CONCLUSION: Less than half of healthcare workers reported willingness to be vaccinated before the campaign start, but proportions varied greatly depending on profession and workplace. Strategies with clear and objective messages that particularly address the concerns of healthcare workers are needed if their willingness to be vaccinated against COVID-19 is to be further increased.

Seroprevalence of SARS-CoV-2 in healthcare workers from outpatient facilities and retirement or nursing homes in a Swiss canton.

BACKGROUND: Healthcare workers are more frequently exposed to SARS-CoV-2 than the general population. Little is known about healthcare settings outside of hospitals. We studied the seroprevalence of SARS-CoV-2 among healthcare workers in outpatient facilities and retirement or nursing homes in the Canton of Solothurn, Switzerland in the first wave of the COVID-19 pandemic. METHODS: Longitudinal seroprevalence study among healthcare workers with examinations at baseline and 2 months between June and September 2020. The Abbott SARS-CoV-2 IgG and Liaison/Diasorin SARS-CoV-2 S1/S2 IgG assay were used to detect antibodies against SARS-CoV-2. All participants provided demographic information. We report descriptive statistics and calculated the seroprevalence with 95% confidence intervals. RESULTS: We included 357 healthcare workers; their median age was 43 years (interquartile range 29-54), and 315 (88.2%) were female. Forty-nine (13.7%) were physicians, 87 (24.4%) practice assistants and 221 (61.9%) nurses. Overall seroprevalence among healthcare workers in outpatient facilities and retirement or nursing homes was 3.4% (12/357). The 12 seropositive healthcare workers were all nurses (12/221, 5.5%); 11 worked at retirement or nursing homes and one at the hospital's outpatient clinic. Symptoms such as loss of smell or taste, shortness of breath, and fever were more prevalent among seropositive healthcare workers than seronegative healthcare workers. No close contact had detectable antibodies against SARS-CoV-2. CONCLUSIONS: Seroprevalence among healthcare workers was low, but higher among nursing staff of retirement or nursing homes. Healthcare workers at private practices were able to protect themselves well during the first wave of the COVID-19 pandemic.

Losing ground at the wrong time: trends in self-reported influenza vaccination uptake in Switzerland, Swiss Health Survey 2007-2017.

OBJECTIVES: We studied time trends in seasonal influenza vaccination and associations with socioeconomic and health-related determinants in Switzerland, overall and in people aged ≥65 years. DESIGN: Three cross-sectional surveys. PARTICIPANTS: Individuals who participated in the Swiss Health Surveys 2007, 2012 and 2017. We calculated the proportion reporting influenza vaccination in the last 12 months, and performed multivariable logistic regression analyses. RESULTS: We included 51 582 individuals in this analysis. The median age was 49 years (IQR 25-64), and 27 518 were women (53.3%). The proportion of reporting a history of influenza vaccination overall was 31.9% (95% CI 31.4 to 32.4); and dropped from 34.5% in 2007 to 28.8% in 2017. The uptake of vaccination within the past 12 months was 16% in 2007 and similar in 2012 and 2017 (around 14%). In people with chronic disease, uptake dropped from 43.8% in 2007 to 37.1% in 2012 and to 31.6% in 2017 (p<0.001). In people aged ≥65 years, uptake dropped from 47.8% in 2007 to 38.5% in 2012 to 36.2% in 2017 (p<0.001). In logistic regression, self-reported vaccination coverage decreased in the 65-75 years old (adjusted OR (aOR) 0.56, 95% CI 0.48 to 0.66 between 2007 and 2012; aOR 0.89, 95% CI 0.77 to 1.03 between 2012 and 2017). Uptake was positively associated with the ≥65 age group, living in French-speaking and urban areas, history of smoking, bad self-reported health status, private/semiprivate health insurance, having a medical profession and having any underlying chronic disease. CONCLUSION: Influenza vaccination coverage was low in older and chronically ill persons. Significant efforts are required in preparing for the influenza season 2020/2021 to reduce the double burden of COVID-19 and seasonal influenza. These efforts should include campaigns but also novel approaches using social media.