Objectives: The aim of the present paper is to assess the influence of demographic, muscle enzymes, JDM scores and treatment on non-adjuvanted influenza A H1N1/2009 vaccine immunogenicity in juvenile dermatomyositis (JDM) patients.
Methods: Thirty JDM patients and 81 healthy age-matched controls were vaccinated. All participants were evaluated pre- and 21 days post-vaccination and serology for anti-H1N1 was performed by haemagglutination inhibition assay. Muscle enzymes, JDM scores and treatment were evaluated before and after vaccination. Adverse events were reported.
Results: After immunisation, seroconversion rates were significantly lower in JDM patients compared to age-matched controls (86.7 vs. 97.5%, p=0.044), whereas seroprotection (p=0.121), geometric mean titres (GMT) (p=0.992) and factor increase (FI) in GMT (p=0.827) were similar in both groups. Clinical and laboratorial evaluations revealed that JDM scores and muscle enzymes remained stable throughout the study (p>0.05). A higher frequency of chronic course was observed in non-seroconverted compared to seroconverted (100% vs. 27%, p=0.012). Regarding treatment, a lower rate of seroconversion was observed in patients under prednisone>20mg/day (50% vs. 4%, p=0.039), and in those treated with a combination of prednisone, methotrexate and cyclosporine (50% vs. 4%, p=0.039). Local and systemic vaccine adverse events were mild and similar in patients and controls (p>0.05).
Conclusions: This study identified that chronic course and immunosuppressive therapy are the major factors hampering seroconversion in JDM, suggesting that a specific protocol may be required for this subgroup of patients. In spite of that, a single dose of non-adjuvanted influenza A/H1N1 2009 vaccine was generally seroprotective in this disease with no evident deleterious effect in disease itself (ClinicalTrials.gov, no. NCT01151644).