Omicron BA.1/1.1 SARS-CoV-2 Infection among Vaccinated Canadian Adults
Patrick E. Brown, Sze Hang Fu, Aiyush Bansal, Leslie Newcombe, Karen Colwill, Geneviève Mailhot, Melanie Delgado-Brand, Anne‐Claude Gingras, Arthur S. Slutsky, Maria Pasic, Jeffrey Companion, Isaac I. Bogoch, Ed Morawski, Teresa Lam, Angus Reid, Prabhat Jha
Abstract
C o r r e s p o n d e n c e Omicron BA.1/1.1 SARS-CoV-2 Infection among Vaccinated Canadian Adults To the Editor: The incidence of the omicron BA.1/1.1 variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which rapidly spread worldwide even among vaccinated persons, is incompletely defined. 1 We quantified the incidence of SARS-CoV-2 infection during the initial omicron BA.1/1.1 variant wave among Canadian adults 2 and the contribution of previous infection and concurrent vaccination to agespecific active immunity (Fig. S1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org). 3 From May 2020 through March 2022, in the Action to Beat Coronavirus (Ab Driedblood-spot samples that had been obtained by the participants were tested with highly sensitive and specific chemiluminescence-based enzyme-linked immunosorbent assays targeting the spike protein, receptor-binding domain, and nucleocapsid (N) protein. Vaccines that have been used in Canada contain only spike protein and thus should not elicit N protein positivity. Approval for the study was obtained from the institutional review board at Unity Health Toronto.