Background: Patients with inflammatory bowel disease (IBD) who are treated long-term with immunosuppressive drugs can experience a decrease in their overall resistance to infections, including influenza. The purpose of this study was to evaluate the humoral response in children with IBD after being vaccinated against influenza.
Material/Methods: Children with IBD were vaccinated with split inactivated vaccine. They were divided into 2 groups: children treated with anti-inflammatory medications and children treated with 5-acetylsalicylic acid along with immunomodulatory therapy. Antihemagglutinin (anti-HA) and antineuraminidase (anti-NA) antibodies were assessed before vaccination and 1 and 6 months after vaccination.
Results: Anti-HA and anti-NA antibodies 1 and 6 months after vaccination were higher than before vaccination. In the patients treated with anti-inflammatory medications, the protection rate (PR) attained the highest level for antigens A/H1N1 and B 6 months after vaccination. However, for A/H3N2 the result was 88.9% at 1 and 6 months after vaccination. In the patients who received immunomodulatory medications, the highest PR was noted 6 months after vaccination (47.6–90.5%). The response rate (RR) in patients who were treated with the anti-inflammatory medications alone remained the same 1 and 6 months after vaccination. In patients who received the immunomodulatory regimen, the highest RR was recorded 6 months after vaccination (47.6–76.2%).
Conclusions: Response to vaccination was satisfactory, although not for all vaccine antigens, especially in patients treated with immunomodulatory medications. The higher levels of RP and RR 6 months after vaccination compared with 1 month after vaccination lends support to the argument that IBD patients should be vaccinated as soon as vaccine is available in a season.

Keywords: Influenza, Human - prevention & control, Influenza Vaccines - immunology, Influenza A virus - immunology, Inflammatory Bowel Diseases - virology, Immunization, Immunity, Humoral - immunology, Hemagglutinin Glycoproteins, Influenza Virus - immunology, Epidemics - prevention & control, Child, Antibodies, Viral - immunology, Adolescent, Neuraminidase - immunology, Poland - epidemiology, Seasons