A fourth dose of the COVID-19 mRNA vaccine effectively reduced the risk of SARS–CoV-2 infection and severe COVID-19 infection in patients with systemic autoimmune rheumatic diseases receiving therapy with disease-modifying antirheumatic drugs (DMARDs), according to a recent study published by Hanberg et al in The Lancet Rheumatology. In an emulated target trial, investigators used the Mass General Brigham health-care system to analyze the data of 4,305 patients with systemic autoimmune rheumatic diseases who were prescribed DMARDs and either received (n = 3,126) or did not receive (n = 1,179) a fourth dose of a COVID-19 mRNA vaccine from January 16 to June 11, 2022. The primary outcome of the trial was a COVID-19 virus infection, and the secondary outcome was a severe infection. After a median follow-up of 135 and 65 days in those who had received and not received the vaccines, respectively, the investigators found that patients who received a fourth dose of the COVID-19 mRNA vaccine were less likely to experience infections as well as COVID-19–related hospital admissions and mortality compared with those who did not receive a fourth dose. The investigators urged patients with systemic autoimmune rheumatic diseases to remain up to date on their COVID-19 vaccines.