Corona Immunitas, a nation-wide programme of testing has been tracking the percentage of Switzerland’s population with antibodies against the SARS-CoV-2 virus. 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 in June, July, August and September 2020, 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 is similar or higher than the population-wide average. For example, in Basel, 16% of those over 64 have 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.
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 another 100,000 or more 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 infected do not return to normal health within 6 months. A similar study in the UK found a 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 overall rate had dropped to 10% after 12 weeks. It seems that time heals many long Covid patients. However, many questions remain.