Corona Immunitas, a nation-wide testing programme has been tracking the percentage of Switzerland’s population with antibodies against the SARS-CoV-2 virus over time. Since the second wave of the pandemic, the percentage of the population with antibodies has more than doubled in many of the cantons covered by the study.
A sharp rise in antibody rates can be seen when comparing rates found before the second wave with rates recorded more recently after the peak of the second wave.
Cantons with the highest rates of seropositivity from the latest round of studies include Vaud (25%), Geneva (21%), Fribourg (20%), Luzern (18%) and Neuchâtel (17%). Rates were lower in Ticino (16%), Bern (14%), Basel (13%) and Zurich (8%).
Cantons with the highest rates have seen the steepest rises – see figure 1. Vaud (10% -> 25%), Geneva (8% -> 21%), Fribourg (8% -> 20%) and Neuchâtel (5% -> 17%) have all risen by at least 12 percentage points. By contrast, rates in Basel (6% -> 13%) and Zurich (3% -> 8%) have only risen by 7 and 5 percentage points.
Compared to all of the other cantons covered, Geneva stands out for its exceptionally low rate of infection among those over 64 compared to the general population. In Geneva, seropositivity among this group was 11%, much lower than the overall rate of 21% – see figure 2. Across most other cantons the rate among this age group was similar to or higher than the population-wide average. For example, in Basel, 16% of those over 64 had antibodies compared to an average of 13% overall.
Geneva’s relatively low infection rate among those over 64 has likely helped to keep its infection fatality rate (IFR) down – based on Geneva’s latest seropositivity estimate the IFR there is 0.7% (705 / 20.5% x 500,000). With vaccines now on the scene, Geneva has a chance to lock in some of this advantage. By the end of February 2021, Geneva had made good progress on this, having administered 94 shots per 100 people over the age of 80 and 53 per 100 among those between 69 and 80.
Overall, 17% of the Swiss population may now have antibodies, according to Corona Immunitas. However, getting to these higher antibody rates has involved around 8,000 additional deaths and left possibly another 100,000 or more patients with long Covid, an illness that causes a range of symptoms that is still poorly understood.
According to a recent study by Corona Immunitas, 26% of those with Covid-19 had not returned to normal health within 6 months. A similar study in the UK found that 22% had long Covid for up to 5 weeks, with higher rates between the ages of 24 and 69. Encouragingly, the same data showed that the percentage with long Covid symptoms had dropped to 10% after 12 weeks. What happens over longer time spans remains unclear.