Immune response to influenza A/H1N1 vaccine in inflammatory bowel disease patients treated with anti TNF-α agents: Effects of combined therapy with immunosuppressants.

BACKGROUND AND AIMS: Our first objective was to evaluate the immune response to the adjuvanted 2009 A/H1N1 pandemic (pH1N1) vaccine in inflammatory bowel disease (IBD) patients treated with anti-TNF-α alone or combined with immunosuppressants (IS). Second and third aims were the safety of pH1N1 vaccine and the effects on IBD clinical activity. METHODS: 36 patients with Crohn's disease (CD) and 26 with ulcerative colitis (UC) and thirty-one healthy control (HC) subjects were enrolled. 47 patients were on anti TNF-α maintenance monotherapy and 15 on anti TNF-α combined with IS. Sera were collected at baseline (T0) and 4weeks after the vaccination (T1) for antibody determination by hemagglutination inhibition (HAI). Disease activity was monitored at T0 and T1. RESULTS: Seroprotective titers (≥1:40) in patients were comparable to HC. Seroconvertion rate (≥4 fold increase in HAI titer) was lower than HC in IBD patients (p=0.009), either on anti TNF-α monotherapy (p=0.034) or combined with IS (p=0.011). Geometric mean titer (GMT) of antibodies at T1 was significantly lower in patients on combined therapy versus those on monotherapy (p=0.0017) and versus HC (p=0.011). The factor increase of GMT at T1 versus T0 was significantly lower in IBD patients versus HC (p=0.042), and in those on combined immunosuppression, both versus monotherapy (p=0.0048) and HC (p=0.0015). None of the patients experienced a disease flare. CONCLUSION: Our study has shown a suboptimal response to pH1N1 vaccine in IBD patients on therapy with anti TNF-α and IS compared to those on anti-TNF-α monotherapy and HC.