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BACKGROUND: Given their high-risk resident population, nursing homes were critical institutions in the COVID-19 pandemic, calling for continued monitoring and vaccine administration to healthcare workers and residents. Here, we studied long-term severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity in vaccinated and unvaccinated healthcare workers and residents of a nursing home in Switzerland between February 2021 and June 2022. METHODS: Our study comprised 45 participants, of which 39 were healthcare workers and six were residents. All participants were offered a maximum of three mRNA vaccine doses (Pfizer/BioNTech, BNT162b2) in December 2020, January 2021, and November/December 2021. Thirty-five participants received three vaccinations, seven either one or two, and three remained unvaccinated. We collected four blood samples: one in March 2021 and three during follow-ups in November 2021, February 2022, and June 2022. We performed a multifactorial serological SARS-CoV-2 assay (ABCORA) for immunoglobulin G, A, and M responses to spike (receptor-binding domain, S1, and S2) and nucleocapsid (N) proteins. Furthermore, we assessed predicted neutralisation activity based on signal over cutoff in ABCORA. We collected epidemiological data from participants via a standardised questionnaire. RESULTS: Thirty-two (71%) of the 45 participants showed hybrid immunity from combined vaccination and previous infection; 10 (22%) had only vaccine-induced immunity; and three (7%) had only post-infection immunity. Participants with hybrid immunity showed the highest predicted neutralisation activity at the end of the study period (median Sum S1 = 273), and unvaccinated participants showed the lowest (median Sum S1 = 41). Amongst participants who reported a SARS-CoV-2 infection, median Sum S1 levels increased with the number of vaccinations (p = 0.077). The healthcare worker group showed a significant time-dependent decrease in median Sum S1 after base immunisation (93% decrease, p = 0.0005) and the booster dose (26% decrease, p = 0.010). Predicted neutralisation activity was lower amongst residents (adjusted ratio of means [AM] = 0.7, 95% confidence interval [CI] = 0.3–1.0) and amongst smokers (AM = 0.5, 95% CI 0.3–0.8). Activity increased with the number of vaccinations (booster: AM = 3.6, 95% CI 1.5–8.8; no booster: AM = 2.3, 95% CI 0.9–2.5). Positive SARS-CoV-2 infection status tended to confer higher predicted neutralisation levels (AM = 1.5, 95% CI 0.9–2.5). CONCLUSIONS: Our study of the long-term serological course of SARS-CoV-2 in a nursing home showed that the first SARS-CoV-2 booster vaccine was essential for maintaining antiviral antibody levels. Hybrid immunity sustained SARS-CoV-2 immunity at the highest level. In critical settings such as nursing homes, monitoring the SARS-CoV-2 immune status may guide booster vaccinations.

BACKGROUND: Contact tracing (CT) has played an important role in strategies to control COVID-19. However, there is limited evidence on the performance of digital tools for CT and no consensus on which indicators to use to monitor their performance. We aimed to describe the system and analyse outcomes of CT with a partially automated workflow in the Swiss canton of Solothurn, using key performance indicators (KPIs). METHODS: We describe the process of CT used in the canton of Solothurn between November 2020 and February 2022, including forward and backward CT. We developed 16 KPIs representing CT structure (S1–2), process (P1–11) and outcome (O1–3) based on previous literature to analyse the relative performance of CT. We report the changes in the indicators over waves of SARS-CoV-2 infections caused by several viral variants. RESULTS: The CT team in Solothurn processed 57,363 index cases and 71,809 contacts over a 15-month period. The CT team successfully contacted 99% of positive cases within 24 hours (KPI P7) throughout the pandemic and returned almost all test results on the same or next day (KPI P6), before the delta variant emerged. Three-quarters of contacts were notified within 24 hours of the CT interview with the index (KPI P8) before the emergence of the alpha, delta and omicron variants, when the proportions decreased to 64%, 36% and 54%, respectively. The percentage of new symptomatic cases tested and interviewed within 3 days of symptom onset was high at >70% (KPI P10) and contacts started quarantine within a median of 3 days of index case symptom onset (KPI P3). About a fifth of new index cases had already been in quarantine by the time of their positive test (KPI O1), before the delta variant emerged. The percentage of index cases in isolation by day of testing remained at almost 100% throughout the period of analysis (KPI O2). CONCLUSIONS: The CT in Solothurn used a partially automated workflow and continued to perform well throughout the pandemic, although the relative performance of the CT system declined at higher caseloads. CT remains an important tool for controlling the spread of infectious diseases, but clearer standards should improve the performance, comparability and monitoring of infection in real time as part of pandemic preparedness efforts.

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.

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.

AIMS We studied time trends in seasonal influenza vaccination and assessed associations with socioeconomic and health-related determinants in Switzerland (overall and people aged ≥65 years). METHODS We used data from the Swiss Health Surveys of 2007 and 2012. We calculated the proportion of the population (overall and those ≥65 years old) reporting influenza vaccination in the last 12 months, and performed multivariate logistic regression analyses, presented as adjusted odds ratios (aORs). RESULTS The average overall frequency of people reporting having been vaccinated for influenza in the previous 12 months was 15.2% (95% confidence interval [CI] 14.7–15.7); frequency decreased from 16.4% in 2007 to 14.1% in 2012 (p