Safety, long-term effectiveness, and immunogenicity of varicella vaccination in children with juvenile idiopathic arthritis treated with biologic therapy

To evaluate safety, long-term effectiveness and immunogenicity of varicella vaccination in children with JIA, treated with biologic disease-modifying antirheumatic drugs (bDMARDs). This is a prospective case-control study. VZV-naive patients with JIA on selected bDMARDs (TNFi, IL-6 and IL-1 inhibitors), who were at risk for contracting varicella, had stable disease and normal values of immunoglobulins and lymphocyte populations, were vaccinated against varicella. Adverse events (AEs) and disease activity were followed after vaccination. VZV-specific humoral (VZV-IgG) and cell-mediated immunity (VZV-CMI) were measured at predetermined time points after vaccination by Liaison and intracellular cytokine staining, respectively. Two healthy control (HC) groups comprised 52 healthy children after varicella vaccination and 69 healthy children after varicella infection. 17 patients were vaccinated against varicella (12 on TNFi, 4 on IL-6 inhibitors and 1 on IL-1 inhibitor), of whom 14 patients received both the first and second dose on bDMARDs. No vaccine strain infections or other serious AEs occurred after vaccination. Disease activity increased in 3/17 (18 %) patients following vaccination. Four out of 17 (24 %) patients developed mild breakthrough varicella (BV) 4 months-4.5 years after vaccination, and none of the HC. Fourteen out of 17 (82 %) patients and 50/52 (96 %) vaccinated HC were seropositive after second vaccination and 8/11 (72 %) patients and 42/43 (98 %) vaccinated HC developed VZV-CMI, which persisted longer compared to VZV-IgG. Patients presented lower antibody levels compared to HC. The rate of VZV-IgG decline was comparable between patients and HC after vaccination or infection. Five patients received the third vaccine dose due to primary or secondary vaccine failure, and none of them developed BV. Varicella vaccination was safe and largely immunogenic in our cohort of JIA patients treated with bDMARDs. Although the vaccination was not always fully effective, it prevented severe disease in all vaccinated patients. • Varicella vaccination was safe in JIA patients treated with biologic therapy. • Three out of 17 (18 %) patients had an increase in disease activity after vaccination. • Four out of 17 (24 %) patients got mild breakthrough varicella. • Vaccine immunogenicity in patients was lower compared to healthy controls. • Patients presented VZV-specific cellular immune response after vaccination.