Pandemic unadjuvanted influenza A (H1N1) vaccine in dermatomyositis and polymyositis: immunogenicity independent of therapy and no harmful effect in disease.

The goal of the present study was to evaluate the influence of the influenza A H1N1/2009 vaccine on dermatomyositis/polymyositis (DM/PM) disease parameters and the potential deleterious effect of therapy on immune response. Thirty-seven DM and 21 PM patients (Bohan and Peter's criteria) were gender- and age-matched to 116 healthy controls. Seroprotection, seroconversion, the geometric mean titers (GMTs) and the factor increase (FI) in the GMTs were calculated. Disease safety was determined from a muscle enzyme analysis and the DM/PM scores [patient's visual analog scale (VAS), physician's VAS, manual muscle strength (MMT-8)] evaluated pre- and post-vaccination. The mean age (43.1±9.9 vs. 43.8±8.4 years, p=0.607) and gender distribution (p=1.00) were comparable between the patients and controls. After 21 days, seroconversion (p=0.394), seroprotection (p=0.08), GMT (p=0.573) and the FI in the GMT (p=0.496) were similar in both groups. The disease and muscle parameters remained stable throughout the study, including the creatine kinase (p=0.20) and aldolase levels (p=0.98), the physicians' VAS (p=1.00), the patients' VAS (p=1.00) and the MMT-8 (p=1.00). Regarding the influence of treatment, the seroconversion rates were comparable between the controls and patients undergoing treatment with glucocorticoid (GC) (p=0.969), GC >0.5mg/kg/day (p=0.395) and GC+immunosuppressors (p=0.285). Vaccine-related adverse events were mild and similar in the DM/PM and control groups (p>0.05). Our data support the administration of the pandemic influenza A H1N1/2009 vaccination in DM/PM, as we found no short-term harmful effects related to the disease itself and adequate immunogenicity in spite of therapy. Further studies are necessary to identify any long-term adverse effects in patients with these diseases.