The role of serological testing in the COVID-19 response in Switzerland

Executive summary

Serological studies, performed on blood samples, have the potential to provide information about the true number of people who have had a SARS-CoV-2 infection. The data allow robust estimates of infection mortality and morbidity in the general populationand in subgroups at increased risk of exposure. At the individual level, serological tests are proposed as a means to identify individuals who have developed immunity to SARS-Cov-2 and can return to work with low risk (“immunity passport”). This policy brief reviews the potentials and limitations of serology in Switzerland and outlines the priorities for future research.

The use of rapid to detect SARS-CoV-2 antibodies at the individual level is currently not indicated:

• Prevalence of infection is low
• The available tests have not been fully validated
• There will be with many false positives if specificity is below 100%
• Neutralising effect of antibodies not established.

The issue of “immunity passports” is problematic from a medical and ethical point of view. A recent study in Geneva established that the seroprevalence at the population level is low (around 5%), despite the high incidence of COVID-19 in Geneva compared to other cantons. The focus for research at the population level should, therefore, be on subpopulations at higher risk of infection. Test accuracy studies of different test types are another priority. Immunological studies of cellular and humoral immune response to SARS-CoV-2, to establish putative immune correlates of protection and the correlations between disease severity and antibody response, and to examine the duration of immunity are another important priority.