Vaccine-induced and hybrid immunity against the B.1.617.2 and B.1.1.529 variants : a test negative case-control study in Belgium, Catteau, Lucy, Braeye Toon, Hubin Pierre, Billuart Matthieu, Haarhuis Freek, Stouten Veerle, Van Loenhout Joris, and Wyndham-Thomas Chloé , Apr 2022, (2022)