Original article Protective effect of A/H1N1 vaccination in immune-mediated disease—a prospectively controlled vaccination study

Objectives. To assess the 2009 influenza vaccine A/H1N1 on antibody response, side effects and disease activity in patients with immune-mediated diseases. Methods. Patients with RA, SpA, vasculitis (VAS) or CTD (n = 149) and healthy individuals (n = 40) received a single dose of adjuvanted A/H1N1 influenza vaccine. Sera were obtained before vaccination, and 3 weeks, 6 weeks and 6 months thereafter. A/H1N1 antibody titres were measured by haemagglutination inhibition (HAI) assay. Seroprotection was defined as specific antibody titre51: 40, seroconversion as 4-fold increase in antibody titre. Results. Titres increased significantly in patients and controls with a maximum at Week 3, declining to levels below protection at Month 6 (P< 0.001). Seroprotection was more frequently reached in SpA and CTD than in RA and VAS (80 and 82 % and 57 and 47%, respectively). There was a significantly negative impact by MTX (P< 0.001), rituximab (P = 0.0031) and abatacept (P = 0.045). Other DMARDs, glucocortic-oids and TNF blockers did not significantly suppress response (P = 0.06, 0.11 and 0.81, respectively). A linear decline in response was noted in patients with increasing age (P<0.001). Disease reactivation possibly related to vaccination was suspected in 8/149 patients. No prolonged side effects or A/H1N1 infections were noted. Conclusions. The results show that vaccination response is a function of disease type, intensity and character of medication and age. A single injection of adjuvanted influenza vaccine is sufficient to protect a high percentage of patients. Therefore, differential vaccination recommendations might in the future reduce costs and increase vaccination acceptance