title: Serological response to the 2009 H1N1 influenza vaccination in patients with inflammatory bowel disease.
abstract: BACKGROUND
  Influenza vaccination is recommended for patients with inflammatory bowel disease (IBD). The 2009 H1N1 influenza vaccine produced seroprotection rates of >85% in the general population but there are no data on the immunogenicity of the vaccine in patients with IBD.
  
  
  METHODS
  An observational prospective open-label study was conducted to examine the immunogenicity of the 2009 H1N1 influenza vaccine in 108 patients with IBD. Patient details, medications and disease activity were recorded. Pre- and post-vaccination haemagglutinin inhibition titres and geometric mean titres were measured. A functional assay of T lymphocyte activity was measured at vaccination in a subset of patients as an alternative measure of immunosuppression. Subjects were followed for 6 months post-vaccination.
  
  
  RESULTS
  Of 108 patients enrolled, 105 completed the study. The post-vaccination seroprotection rate was 50%. Immunosuppressed subjects had a lower rate of seroprotection than non-immunosuppressed subjects (44% vs 64%, p=0.06). The proportion with seroprotection was significantly lower in subjects on combination immunosuppression than in those receiving no immunosuppression (36% vs 64%, p=0.02). Patients receiving combined immunosuppression had a significantly lower fold increase in geometric mean titres than those on monotherapy immunosuppression (3.5 vs 11.5, p=0.03). An assay of T lymphocyte activity was performed in a subgroup of 48 subjects. Those with intermediate activity had lower seroprotection than those with high activity (28% vs 61%, p=0.02). The vaccine was well tolerated.
  
  
  CONCLUSIONS
  Patients with IBD vaccinated with the 2009 H1N1 influenza vaccine had a low rate of seroprotection, particularly among those who were immunosuppressed. Although there is a need for studies of the clinical benefit of vaccines in this population, patients with IBD need to be aware of this reduced immunogenicity.
authors.affiliation: Crohn's and Colitis Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. gcullen@bidmc.harvard.edu
authors.forename: Garret
authors.initials: G
authors.lastname: Cullen
authors.forename: Caroline
authors.initials: C
authors.lastname: Bader
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Korzenik
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Sands
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007108:Immune Tolerance; D007111:Immunity, Cellular; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy / Q000276:immunology*; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013601:T-Lymphocytes / Q000276:immunology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007166:Immunosuppressive Agents; D007252:Influenza Vaccines