Vaccination is a current strategy used to prevent infections in patients with immune-mediated rheumatic diseases. However, the use of live-attenuated vaccines prepared from living microorganisms in these patients should be avoided due to the risk of acquiring infections. The present study aimed to investigate the efect of the yellow fever (YF) vaccine (a live-attenuated vaccine) in 12 patients with rheumatoid arthritis (RA). The sample comprised 12 patients (9 females and 3 males; mean age 52.2±6.5 years) with RA, who inadvertently received fractionated 17D yellow fever vaccination during an outbreak of this disease. In this cohort, 10 were administered lefunomide; 7 were administered methotrexate; 6 were administered prednisone (median dose of 5.0 mg/day); 6 took biologic drugs; and 1 took tofacitinib. All but one patient (used rituximab, prednisone, and methotrexate) seroconverted. None of them developed clinical signs of infection after the procedure. The fractionated dose of the YF vaccine is efective and safe in the observed sample.