One major concern in the management of the COVID-19 pandemic has been to ensure the protection of certain categories of population considered to be at especially high risk in the event of an infection. This article gives an overview of the legal status of the «vulnerable» person in Switzerland and explores the role of the treating physician in this context, particularly with regard to labour law. The physician will have to assess the status of «vulnerable person» and, where applicable, issue a vulnerability certificate that can be presented to the employer. In the face of a legal framework that is often ambiguous and in continuous evolution, this role places significant responsibility on the physicians, who will need to ensure that they stay within a clinical evaluation and the scope of their expertise. Accepted practices in relation to medical certificates for work incapacity may act as valuable guidance.