Bruggmann, P., O. Senn, A. Frei, M. A. Puhan, J. Fehr, and L. Falcato. “High SARS-CoV-2 Seroprevalence But No Severe Course of COVID-19 Disease Among People on Opioid Agonist Treatment in Zurich: a Cross-Sectional Study”. Swiss Medical Weekly, vol. 152, no. 0102, Jan. 2022, p. w30122, doi:10.4414/SMW.2022.w30122.