COVID-19 infection and efficacy of vaccination in patients with rheumatic diseases during Omicron outbreak in South Korea: a prospective cohort study

OBJECTIVES: This study aims to investigate COVID-19 epidemiological data in patients with autoimmune inflammatory rheumatic diseases (AIRDs) during Omicron wave and to identify clinical factors associated with infection, including COVID-19 vaccination. METHODS: This prospective longitudinal study was performed between January and October 2022 in South Korea. Patients were classified into AIRD and non-AIRD groups according to their underlying diseases. COVID-19 status, date of confirmed infection and vaccination status were captured from the patient survey and national database. The COVID-19 incidence during the study period was examined and compared between the two groups. The effect of clinical factors on the infection rate was analysed in the AIRD group. RESULTS: A total of 1814 patients (1535 and 279 in the AIRD and non-AIRD groups, respectively) were analysed. During the study period, 857 COVID-19 cases were reported in 834 patients (46.0%). The infection rates in the AIRD and non-AIRD groups were comparable. In the AIRD group, older age (≥70 years) and glucocorticoid use were significantly associated with a lower rate of COVID-19 infection. The third booster vaccination significantly lowered the incidence of COVID-19 (adjusted HR 0.85 (95% CI 0.73 to 0.99)), and the prophylactic effect was more evident in patients aged <70 years (0.81 (95% CI 0.69 to 0.95), p value for interaction 0.036). CONCLUSION: The risk of SARS-CoV-2 infection with the Omicron variant did not increase in patients with AIRDs. The third booster vaccination regimen decreased the infection rate in patients aged <70 years.