COVID-19 vaccine effectiveness against omicron (B.1.1.529) variant infection and hospitalisation in patients taking immunosuppressive medications: a retrospective cohort study

Background: There is a scarcity of research regarding the effectiveness of the mRNA-1273 (Moderna) and BNT162b2 (Pfizer-BioNTech) COVID-19 vaccines in patients taking immunosuppressant medications, and no data are published to date pertaining to their effectiveness against omicron (B.1.1.529) variant SARS-CoV-2 infection and hospitalisation. We aimed to assess the relationship between immunosuppressive medications, mRNA vaccination, omicron infection, and severe COVID-19 outcomes (ie, hospitalisation, ICU admission, death). Methods: We did a retrospective cohort study and included vaccinated and unvaccinated people aged 18 years or older in the Michigan Medicine health-care system, USA, during the omicron-dominant period of the pandemic (Dec 16, 2021–March 4, 2022). We collected data from electronic health records (demographics, diagnoses, medications) combined with immunisation data from the Michigan State Registry to determine vaccination status, and we collected COVID-19-related hospitalisation data by chart review. We used a Cox proportional hazards model based on calendar time to assess the effectiveness of the mRNA-1273 and BNT162b2 vaccines in people taking immunosuppressive medications (conventional synthetic disease-modifying antirheumatic drugs [DMARDs], biologic DMARDs, or glucocorticoids within the past 3 months), while controlling for participant characteristics. Using the same model, we assessed the effect of different classes of medication such as immunosuppressive DMARDs, immunomodulatory DMARDs, and glucocorticoids on SARS-CoV-2 infection and hospitalisation due to COVID-19. All analyses were done using complete cases after removing participants with missing covariates. Findings: 209 492 people were identified in Michigan Medicine, including 165 913 who were vaccinated and 43 579 who were unvaccinated. 41 078 people were excluded because they were younger than 18 years, partially vaccinated, had received a vaccine other than the two vaccines studied, or had incomplete covariate data. 168 414 people were included in the analysis; 97 935 (58%) were women, 70 479 (42%) were men, and 129 816 (77%) were White. 5609 (3%) people were taking immunosuppressive medications. In patients receiving immunosuppressants, three doses of BNT162b2 had a vaccine effectiveness of 50% (95% CI 31–64; p<0·0001) and three doses of mRNA-1273 had a vaccine effectiveness of 60% (42–73; p<0·0001) against SARS-CoV-2 infection. Three doses of either vaccine had an effectiveness of 87% (95% CI 73–93; p<0·0001) against hospitalisation due to COVID-19. Receipt of immunosuppressive DMARDs (hazard ratio 2·32, 95% CI 1·23–4·38; p=0·0097) or glucocorticoids (2·93, 1·77–4·86; p<0·0001) and a history of organ or bone marrow transplantation (3·52, 2·01–6·16; p<0·0001) were associated with increased risk of hospitalisation due to COVID-19 compared with those who had not received immunosuppressive medications or transplant. Interpretation: People taking immunosuppressive DMARDs or glucocorticoids are at substantially higher risk of hospitalisation due to COVID-19 than the general population. However, the mRNA-1273 and BNT162b2 vaccines remain effective within this group, and it is important that patients taking these medications remain up to date with vaccinations to mitigate their risk. Funding: National Institute of Allergy and Infectious Diseases, National Institutes of Health.