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P259. Influenza A H1N1 vaccine is safe and effective in patients with inflammatory bowel disease treated with thiopurines and TNF-α blockers

I. Dotan1,2, M. Mandelboim3,2, H. Shaharabani4, R. Kariv1,2, E. Tiomny1,2, J. Pfeffer1,2, S. Fishman1,2, E. Hezkelovich1, E. Meirovithz1,2, M.J. Schwaber5,2, Z. Halpern1,2

1Department of Gastroenterology and Liver Diseases, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel; 2Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; 3Central Virology Laboratory, Ministry of Health, Chaim Sheba Medical Center, Ramat Gan, Israel; 4Central Virology Laboratory, Ministry of Health, Chaim Sheba Medical Center, Ramat Gan, Israel; 5National Center for Infection Control, Ministry of Health, Tel Aviv, Israel

Aim: To prospectively assess the response to influenza A H1N1 (swine influenza) vaccine in inflammatory bowel disease (IBD) patients who are treated with thiopurines and TNF-α blockers.

Materials and Methods: IBD patients were prospectively recruited during November 2009-January 2010. One dose of the adjuvanted influenza A H1N1 vaccine (A/California/7/2009, Focetria®, Novartis) was administered intramuscularly (week 0). Demographic data were recorded. Serologic response was assessed before vaccination and after 4 weeks using hemagglutination inhibition assay. Patients with an IgG titer of ≥1:40 were considered immune. Clinical activity scores and side effects, laboratory tests and lymphocyte subpopulations were assessed before (week 0) and 4 weeks following vaccination.

Results: Forty-one IBD patients (33 with Crohn's disease) were recruited. Average age: 39.7±9.3 years, 58.3% males. Treatment at week 0 included thiopurines (azathioprine or 6-mercaptopurine; 24 patients), TNF-α blockers (infliximab or adalimumab; 9), combined thiopurines and TNF-α blockers (7) and steroids (1). Significant increase in antibody titers to ≥1:640 at week 4 was observed (p < 0.001 vs. week 0). All but two patients attained immunity against influenza A H1N1. These patients were treated with adalimumab (2) and 6-mercaptopurine (1). Thiopurine or TNF-α blockers alone were associated with 3.5±0.3 and 3.6±1.7 fold increase in antibody titers, respectively. Combined thiopurine and TNF-α therapy was associated with a lower increase in antibody titers, however this was not statistically significant (1.3±0.8. p = NS compared to either therapy alone). Seven patients were already immune at week 0. In this patients subgroup the increase in antibody titers was less significant (p = 0.06 vs. week 0) compared to those who were nonimmune prior to vaccination (p = 0.001 vs. week 0). Prior seasonal influenza vaccine was administered to 18 patients. Four of those (22%) were immune to influenza A H1N1 before vaccination. Nevertheless, the response to influenza A H1N1 vaccine was unaffected by prior vaccination against seasonal influenza. The most common side effect was local response (pain or erythema, 27% of patients). In patients receiving thiopurines significantly lower white blood cell counts were observed and all lymphocyte subpopulations except for CD56+ and CD8+ were similarly decreased. No significant changes in clinical activity scores or C-reactive protein levels after vaccination were observed.

Conclusions: A single dose of influenza A H1N1 vaccine generated good humoral responses in thiopurine and TNF-α blockers treated IBD patients. IBD patients can be safely and effectively vaccinated against influenza A H1N1.