ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
Subject(s)
COVID-19 , Adult , Aged , COVID-19 Vaccines , Cross-Sectional Studies , Female , Health Personnel , Humans , Male , Pandemics , SARS-CoV-2 , Surveys and Questionnaires , Switzerland , VaccinationABSTRACT
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.