Objective: To study the immunogenicity, safety and efficacy of influenza vaccine in children with chronic rheumatic diseases (CRD) receiving long-term immunosuppressive therapy.
Methods: Seventy children (F:M 51:19) with CRD (JIA = 49, SLE = 11, other = 10) aged 4-17 yrs and 5 healthy siblings of the patients (aged < 11 yrs) received a "split type" influenza vaccine (Fluarix SB) licensed for the 1999-2000 winter season. Clinical and laboratory evaluation were performed at study entry and at 1, 3 and 6 months after vaccination. Blood samples were collected before and one month after vaccination and antibody titers to A/Beijing, A/Sydney and B/Beijing influenza antigens were measured using a standardized hemagglutination inhibition assay.
Results: Patients were assigned to groups according to the therapeutic regimen [prednisone (PDN), PDN plus 1 disease modifying antirheumatic drug (DMARD), PDN plus 2 DMARDs and 1 or 2 DMARDs without PDN]. 5/70 patients reported local (3) or systemic (2) reactions and 1/5 siblings local reaction. Nine more patients reported mild upper respiratory tract symptoms 1-4 weeks post-vaccination. No patient was found to fulfill criteria for deterioration or flare of the underlying disease. At completion of vaccination 97.14% of patients developed protective HI titers to A/Beijing, 100% to A/Sydney and 80% to B/Beijing. No significant difference in the mean geometric titers was found between patients with different therapeutic regimens or age or between those with JIA or SLE. Disease activity was not related with response or non-response to B/Beijing. No patient reported "flu-like" symptoms during the 6-month period of follow-up.
Conclusion: The results of our study indicate that children with CRD receiving long-term immunosuppressive therapy at conventional doses respond to influenza vaccination similarly to healthy children without serious adverse reactions or disease flares regardless of their age, type of CRD or therapeutic regimen.