Nyberg, T, Ferguson, N M, Nash, S G, Webster, H H, Flaxman, S, Abbott, S & et, A 2022, ' Comparative analysis of the risks of hospitalisation and death associated with SARS-CoV-2 omicron (B.1.1.529) and delta (B.1.617.2) variants in England : a cohort study ', Lancet, vol. 399, no. 10332, pp. 1303-1312 . https://doi.org/10.1016/S0140-6736(22)00462-7