Objectives We aim to assess the protective role of the influenza vaccine by analyzing the association between respiratory infections occurrence and humoral response to influenza A (H1N1) infection in patients with autoimmune rheumatic diseases.

Methods Our study included 30 patients with systemic lupus erythematosus (SLE), 37 with rheumatoid arthritis (RA) and 32 with Sjögren's Syndrome (SjS). In November 46 patients with stable status of underlying diseases were immunized with an inactivated trivalent split vaccine (15 μg HA A/California/7/2009 (H1N1), 15 μg HA A/Pert/16/2009 (H3N2) and 15 μg/HA B Brisbane/60/2008) whereas 52 patients did not accept the proposed vaccination. In the following six months parameters of disease activity (from the date of vaccination until April 2011) and the titer of antibodies against influenza A H1N1 were monitored. We used hemagglutination inhibition test (according to the method of the Center for Disease Control and Prevention (CDC)) with antigen A/California/7/2009 influenza virus (H1N1), and turkey erythrocytes for the detection of antibodies against the A H1N1. Value of seroprotective titer (ST) was defined as ≥32. Importance of predisposing factors for influenza occurrence (i.e. previous respiratory infections and vaccinations in last five years) was also analyzed.

Results The incidence of viral and bacterial infections among vaccinated patients was significantly lower, compared to the non-vaccinated group. Influenza occurrence was significantly associated with previous respiratory infections (p=0.001). The mean titer of antibodies was highest in SLE patients and significantly higher in all vaccinated patients (p=0.018). Mid-level antibody titer was significantly related to last vaccination in all patients (p=0.001) and has not been proven after removal of last vaccination effects (p=0.227). Similar results were obtained for patients with SLE, while in RA and SjS these correlations were not significant. ST levels for all vaccinated patients (84.17) were significantly higher than in non-vaccinated patients (8.80) (p=0.008) and were associated with last vaccination in all patients and in SLE group (p=0.012, p=0.039 respectively). Highest levels were observed in vaccinated SLE patients (141.05) and were significantly higher than in non-vaccinated patients (p=0.002). Seroprotective rate for all vaccinated patients was 48% compared to 15% in unvaccinated (p=0.014) and it was highest among SLE patients (53%) (p=0.049). In RA and SjS groups, these differences were not statistically significant. There was no significant difference between three diseases regarding the mean ranks of antibody titer (p=0.418). Previous bronchitis and pneumonia increased influenza risk significantly.

Conclusions Regardless of the differences in the level of antibody titers we have proved that the clinical efficacy of influenza vaccination in observed diseases is significant and very similar, primarily as a protection against influenza and indirectly against secondary bacterial complications.

References

1. Milanovic M, Stojanovich L, Djokovic A, Kontic M, Gvozdenovic E. Influenza vaccination in autoimmune rheumatic disease patients. Tohoku J Exp Med. 2012;229(1):29-34.

Disclosure of Interest : None declared

DOI 10.1136/annrheumdis-2014-eular.2454