[How to conduct public health surveillance? The example of the Observatoire Valaisan de la Santé in Switzerland]. / Comment faire de la surveillance sanitaire? L'exemple de l'Observatoire Valaisan de la Santé en Suisse.

OBJECTIVE: To describe the goals and methods of contemporary public health surveillance and to present the activities of the Observatoire Valaisan de la Santé (OVS), a tool unique in Switzerland to conduct health surveillance for the population of a canton. METHODS: Narrative review and presentation of the OVS. RESULTS: Public health surveillance consists of systematic and continuous collection, analysis, interpretation and dissemination of health data necessary for public health planning. Surveillance is organized according to contemporary public health issues. Switzerland is currently in an era dominated by chronic diseases due to ageing of the population. This "new public health" era is also characterized by the growing importance of health technology, rational risk management, preventive medicine and health promotion, and the central role of the citizen/patient. Information technologies provide access to new health data, but public health surveillance methods need to be adapted. In Switzerland, health surveillance activities are conducted by several public and private bodies, at federal and cantonal levels. The Valais canton has set up the OVS, an integrative, regional, and reactive system to conduct surveillance. CONCLUSION: Public health surveillance provides information useful for public health decisions and actions. It constitutes a key element for public health planning.

Corona Immunitas: study protocol of a nationwide program of SARS-CoV-2 seroprevalence and seroepidemiologic studies in Switzerland.

OBJECTIVES: Seroprevalence studies to assess the spread of SARS-CoV-2 infection in the general population and subgroups are key for evaluating mitigation and vaccination policies and for understanding the spread of the disease both on the national level and for comparison with the international community. METHODS: Corona Immunitas is a research program of coordinated, population-based, seroprevalence studies implemented by Swiss School of Public Health (SSPH+). Over 28,340 participants, randomly selected and age-stratified, with some regional specificities will be included. Additional studies in vulnerable and highly exposed subpopulations are also planned. The studies will assess population immunological status during the pandemic. RESULTS: Phase one (first wave of pandemic) estimates from Geneva showed a steady increase in seroprevalence up to 10.8% (95% CI 8.2-13.9, n = 775) by May 9, 2020. Since June, Zurich, Lausanne, Basel City/Land, Ticino, and Fribourg recruited a total of 5973 participants for phase two thus far. CONCLUSIONS: Corona Immunitas will generate reliable, comparable, and high-quality serological and epidemiological data with extensive coverage of Switzerland and of several subpopulations, informing health policies and decision making in both economic and societal sectors. ISRCTN Registry: https://www.isrctn.com/ISRCTN18181860 .