Vaccine effectiveness against SARS-CoV-2 infection and severe outcomes among individuals with immune-mediated inflammatory diseases tested between March 1 and Nov 22, 2021, in Ontario, Canada: a population-based analysis

BACKGROUND: We estimated COVID-19 vaccine effectiveness against SARS-CoV-2 infection and severe COVID-19 outcomes among individuals with immune-mediated inflammatory diseases in Ontario, Canada. METHODS: In this population-based analysis, we used a test-negative design across four immune-mediated inflammatory disease population-based cohorts, comprising individuals with rheumatoid arthritis, ankylosing spondylitis, psoriasis, and inflammatory bowel disease. We identified all SARS-CoV-2 tests done in these populations between March 1 and Nov 22, 2021 (a period in which there was rapid uptake of vaccines, and the alpha [B.1.1.7] and delta [B.1.617.2] SARS-CoV-2 variants were predominantly circulating in Canada) and separately assessed outcomes of SARS-CoV-2 infection and severe COVID-19 outcomes (hospitalisation due to COVID-19 and death due to COVID-19) for each disease group. We used multivariable logistic regression to estimate the effectiveness of one, two, and three doses of mRNA-based COVID-19 vaccine (BNT162b2 [Pfizer–BioNTech], or mRNA-1273 [Moderna]) among individuals at the time of SARS-CoV-2 testing. FINDINGS: Between March 1 and Nov 22, 2021, we identified 2127 (5·9%) test-positive cases among 36 145 individuals (26 476 [73·2%] were female and 9669 [26·8%] were male) with rheumatoid arthritis tested, 476 (6·1%) test-positive cases among 7863 individuals (4130 [52·5%] were female and 3733 [47·5%] were male) with ankylosing spondylitis tested, 3089 (6·5%) test-positive cases among 47 199 individuals (26 062 [55·2%] were female and 21 137 [44·8%] were male) with psoriasis tested, and 1702 (5·4%) test-positive cases among 31 311 individuals (17 716 [56·6%] were female and 13 595 [43·4%] were male) with inflammatory bowel disease tested. Adjusted vaccine effectiveness of two doses against infection was 83% (95% CI 80–86) in those with rheumatoid arthritis, 89% (83–93) among those with ankylosing spondylitis, 84% (81–86) among those with psoriasis, and 79% (74–82) among those with inflammatory bowel disease. After two vaccine doses, effectiveness against infection generally peaked 31–60 days after vaccination and waned gradually with each additional month. Vaccine effectiveness against severe outcomes after two doses was 92% (95% CI 88–95) in those with rheumatoid arthritis, 97% (83–99) among those with ankylosing spondylitis, 92% (86–95) among those with psoriasis, and 94% (88–97) among those with inflammatory bowel disease. Vaccine effectiveness after a third dose against infection was similar to or higher than after the second dose (ranging from 76% [47–89] to 96% [72–99]), although due to a paucity of events, estimates could not be calculated for some subgroups for severe outcomes. INTERPRETATION: Two vaccine doses were found to be highly effective against both SARS-CoV-2 infection and severe COVID-19 outcomes in patients with rheumatoid arthritis, ankylosing spondylitis, psoriasis, and inflammatory bowel disease during the study period. Research is needed to determine the durability of effectiveness of three doses over time, particularly against emerging variants. FUNDING: Public Health Agency of Canada