18.06.2020

Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study

Epidemiological InfectiologyVirology
Stringhini S et al
Lancet

Main result

The risk of seropositivity was similar between men and women (RR 1.26 [95% CI 1.00-1.58]).

Young children aged 5 to 9 years were estimated to have a lower risk of being HIV-positive (RR 0.32 [0.11-0.63]) than those aged 20 to 49 years. Similarly, people aged 65 years and older had a lower risk (RR 0.50 [0.28-0.78]) of being HIV-positive than those aged 20-49 years.

The risk of seropositivity was similar for men and women (RR 1.26 [95% CI 1.00-1.58]).

These results are consistent with a small but growing body of evidence suggesting that young children are both infected and develop severe disease less frequently than adults, but many uncertainties remain.

It should be noted that the ELISA test used has been validated in an adult population only; whether the IgG response in children is delayed or qualitatively different requires further investigation.

During the 5 weeks of the study, increase in seroprevalence from about 5% to about 11%, which is to be expected given the delay in seroconversion after symptoms (median 10.4 days [IQR 8.1-13.4 ]) and that the peak of the epidemic was reached the week before the start of our survey.

This study also confirms that the cases identified during the acute phase of the disease provide little information on the status of the epidemic. Indeed, they observed that in the community, there were 11 infections for every confirmed case of COVID-19 in Geneva, reflecting the variability in disease severity, access to testing or practices, and care-seeking behaviour.

 

Takeaways

These results suggest that the majority of the Geneva population was not infected during this pandemic wave, despite the high prevalence of COVID-19 in the region (5000 clinical cases reported over <2.5 months in a population of half a million people).

Significantly lower seroprevalence was observed in children aged 5 to 9 years and adults over 65 years of age compared to those aged 10 to 64 years.

These results will be useful for countries considering easing restrictions to curb transmission.

Serological studies such as these are crucial to provide new insights into transmission and the otherwise hidden immunological status of the population.

Strength of evidence Moderate

- Selection bias despite adjustments made using differences in age and gender distribution.
- Preliminary participation rate of 30 to 40%.
- Large sample size
- Possible overestimation of prevalence due to the fact that participants who experienced COVID-19-like symptoms, or those who were less confined during confinement (for example, those not in a risk group) were more likely to participate in the study.

Objectives

Estimated weekly seroprevalence of SARS-CoV-2 antibodies in the population of Geneva, Switzerland, during the epidemic.

Method

Search in PubMed, medRxiv, bioRxiv, arXiv, SSRN, Research Square, Virological and Wellcome Open Research for articles, prepublications and research reports on anti-SARS-CoV-2 IgG seroprevalence, published in English, using the search terms "seroprevalence", "anti-SARS-CoV-2 IgG", "convection antibodies" and similar terms, up to 15 May 2020.

Between April 6 and May 9, 2020, 2834 persons were registered, of which 2766 had given complete data and were included in our analysis. 1454 (52.6%) of the 2766 participants were women; and 123 (4 - 4%) were aged 5-9 years, 332 (12 - 0%) were aged 10-19 years, 1096 (39 - 6%) were aged 20-49 years, 846 (30 - 6%) were aged 50-64 years, and 369 (13 - 3%) were over 65 years of age.

Each participant received three standardized self-administered questionnaires covering risk factors for major lifestyle-dependent chronic diseases, socio-demographic characteristics, educational and employment history and, for women, obstetrical history.

 

 

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