Seroprevalence of SARS-CoV-2 antibodies and development of immunity in the Swiss population – Population-based observational studies to inform policy making (CORONA IMMUNITAS)

For many different stakeholders in Switzerland (including policy, health care professionals, infected, other vulnerable population groups) it is crucial that current and future policy decisions on how to minimize the disease and societal burden of SARS-COV-2 are informed by solid data. This in turn requires knowledge of the nation-wide prevalence of SARS-CoV-2 infection at the level of the population, in different geographical areas and of specific age groups. This knowledge will also help prepare future outbreak responses and is also important to inform future vaccination strategies. In a number of Cantons, studies on the seroprevalence of SARS-CoV-2 antibodies and the extent and duration of immunity are planned or have already started. The interest for such epidemiological studies comes from both Cantonal authorities and scientists who want to learn about the seroprevalence of SARS-CoV-2 antibodies, both in the general population (across age ranges) and in specific groups of persons (e.g. nursing home residents, working in specific sectors of economy, from citizens, etc.).

The scientists of the Swiss School of Public Health (SSPH+) have agreed to coordinate their effort in order to make their data as comparable as possible, to create synergies and reduce redundancies. The goal is to make the studies informative for policy makers on the national and Cantonal level while fully respecting the autonomy of the Cantons and scientists involved (https://www.corona-immunitas.ch/). The main aim of this study is to determine the extent and nature of infection with SARS-CoV-2 in the Canton of Zurich and to contribute to consistent estimates in the Swiss population. The overall objectives addressed nation-wide are:

• To determine the prevalence of the population with SARS-CoV-2 antibodies and the proportion of people with or without COVID-19 attributable symptoms (symptomatic/asymptomatic) in the past showing SARS-CoV-2 antibodies;
• To identify associations of seropositivity with sociodemographic, chronic conditions, exposure, hygiene, behavioral and environmental factors;
• To assess whether SARS-CoV-2 infection re-occurs in people with SARS-CoV-2 antibodies over time, and to determine the proportion of re-infections and the duration of the acquired immunity;
• To determine the proportion of individuals without SARS-CoV-2 antibodies who will experience a SARS-CoV-2 infection;
• To assess how persons in Switzerland adjust their lives and adopt preventive measures to avoid contact with SARS-CoV-2 over extended periods of time;
• To assess how mental health is affected by the threat of the SARS-CoV-2 epidemic and by the preventive measures mandatorily imposed or strongly recommended by health authorities.

Additional objectives specifically addressed by the Canton of Zurich are:

• To assess the course of the serology in a subsample of initially measured seropositive and seronegative persons over time;
• To compare the seroprevalence found in specific populations who are particularly exposed to SARS-CoV-2 due to their work or their circumstances with the seroprevalence in the general population;
• To compare the seroprevalence found in a convenience sample of people who proactively requested an SARS-CoV-2 antibody test with that of the general population, and to assess and compare the psychosocial and behavioral response of this subgroup on the knowledge of the test-result;
• To evaluate whether SARS-CoV-2 infection results in a loss of T cells specific to other common pathogens.

The study details are published here: Corona Immunitas

• Projektwebsite: https://www.corona-immunitas.ch/
• https://pubmed.ncbi.nlm.nih.gov/35929427/
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