Seroprevalence of anti-SARS-CoV-2 IgG antibodies, risk factors for infection and associated symptoms in Geneva, Switzerland: a population-based study

Aude Richard, Ania Wisniak, Javier Perez-Saez, Henri Garrison-Desany , Dusan Petrovic, Giovanni Piumatti, Hélène Baysson, Attilio Picazio, Francesco Pennacchio, David De Ridder, François Chappuis, Nicolas Vuilleumier, Nicola Low, Samia Hurst, Isabella Eckerle, Antoine Flahaul, Laurent Kaiser, Andrew S. Azman, Idris Guessous & Silvia Stringhini.
Seroprevalence of anti-SARS-CoV-2 IgG antibodies, risk factors for infection and associated symptoms in Geneva, Switzerland: a population-based, study, Scandinavian Journal of Public Health, Published on line October 2021, doi:10.1177/14034948211048050

Summary:

Aims: To assess the seroprevalence of anti-SARS-CoV-2 IgG antibodies during the first epidemic wave in the canton of Geneva, Switzerland, as well as risk factors for infection and symptoms associated with seropositivity.

Methods: Between April and June 2020, former participants in the "Health Bus" survey (an annual cross-sectional survey of a representative sample of the population aged 20 to 74 in the canton of Geneva) were invited to take part in the study, along with household members aged over 5 years. Blood samples were tested for anti-SARS-CoV-2 immunoglobulin G. Data were collected using online questionnaires. Seroprevalence was estimated using a Bayesian model taking into account test performance and sampling design.

Results: 8344 participants were included in the study. Adjusted overall seroprevalence was 7.8% (95% confidence interval 6.8-8.9). Seroprevalence was highest among 18-49 year olds (9.5%) and lowest among children aged 5-9 (4.3%) and people over 65 (4.7-5.4%). The risk of seropositivity was significantly lower for retired women and unemployed men than for employed people, and for smokers than for non-smokers. We found no significant association between occupation, level of education or neighbourhood income and the risk of being HIV-positive. The symptom most strongly associated with seropositivity was anosmia/dysgeusia.

Conclusion: Population seroprevalence remained low after the first wave in Geneva. Socioeconomic factors were not associated with seropositivity in this sample. The elderly, young children and smokers were less frequently seropositive, although it is not clear how biology and behaviour explain these differences.

Link to the article in English