Why is antibody testing taking place in six phases?

The aim of the first phase is an early assessment of how the virus has spread in severely affected Swiss cantons (GE, BS, BL, VD and TI). These initial findings will show the state of immunity in the population and uncover differences between regions.

Data from the second phase provide a first estimate of the development of immunity in the Swiss population after the first peak of the pandemic in summer 2020 and the first loosening of the measures.

In the third phase between November 2020 and February 2021 the timing of the spread of the coronavirus and the influence of protective measures on the spread of the virus in the different regions will be studied. In addition, Phase 3 will assess the degree and duration of immunity and evaluate vaccination needs based on the data.

In the fourth phase between end of May and July 2021 the same topics were evaluated as in phase 3 (but after winter 2020/21) and already with partial influence of vaccination. In all phases, questions about quarantine, isolation, the SwissCovid App, behavior and quality of life of the volunteers were answered. The cantons Vaud and Valais have conducted phase 4 later, the so-called phase 4b. Whilst the centrally coordinated part of Corona Immunitas ended with a last questionnaire on 26h of November 2021, the Fast Response Unit was put in place.

As of the end of November 2021, the nationally coordinated digital follow-up was terminated, although some study centers will continue it individually. The so-called Fast Response Unit was established, consisting of the three study centers Ticino, Vaud and Zurich. It should be deployed in case of substantial changes in the pandemic situation - such as omicron is. Therefore, it was decided to conduct another serological testing phase after the peak of the omricron wave together with a digital follow-up (focusing on (re-)infections) in the general population. Because a testing phase had only recently taken place in the canton of Vaud, phase 5 is limited to Ticino and Zurich.

The sixth phase will take place in summer 2022. In addition to the topics from phase 5, this phase will focus on the development of the pandemic situation after extensive easing and on an assessment of the situation before the fall of 2022. The digital follow-up will continue to be conducted in an abbreviated form and, as in phase 5, will in particular query the vaccination status and the (re)infections that have occurred. Because the regional differences due to vaccination and natural infections are becoming smaller, it is not necessary to continue to conduct the surveys in all 14 study centers.