Background
Influenza vaccination is recommended for patients with cardiovascular diseases. The main reason for the low vaccination rates in such patients is insufficient knowledge about vaccination efficacy, including immune response to the vaccine. The aim of this study was to assess humoral response to influenza vaccination in patients with coronary artery disease.
Material and Method
This was a substudy of the randomized prospective double-blind placebo-controlled FLUCAD study on influenza vaccination in the secondary prevention of ischemic coronary events in patients with coronary artery disease. Patients received inactivated subunit vaccine (n=325) or placebo (n=333). Anti-hemagglutinin and anti-neuraminidase antibody levels to the vaccine strains as well as IgM and IgG levels against influenza A and B were measured before administration of vaccine/placebo and after 8-10 weeks in 78 vaccinated and 97 placebo patients.
Results
Post-vaccination antibody titers were significantly higher than before vaccination, with mean increases of 4.9- to 5.7-fold for anti-hemagglutinin and 3.5- to 4.2-fold for neuraminidase antibodies. Post-vaccination protection rates ranged from 56.4 to 60.3% and response rates from 62.8 to 68%. The percentage of patients with significant post-vaccination concentrations of IgG and IgM was higher than before vaccination and amounted to 100% and 88.1% in the case of IgG and 14.3% and 5.2% in the case of IgM in response to influenza A and B, respectively.
Conclusions
At least 60% of the patients achieved high post-vaccination antibody levels sufficient to prevent influenza.

Keywords: Influenza Vaccines - immunology, Double-Blind Method, Hemagglutinin Glycoproteins, Influenza Virus - immunology, Coronary Artery Disease - immunology, Antigens, Viral - immunology, Antibody Formation - immunology, Antibodies, Viral - immunology, Aged, 80 and over, Neuraminidase - immunology, Orthomyxoviridae - immunology