Humoral response to influenza vaccination in HIV-infected patients

Objective: To assess the humoral response in HIV-infected adults immunised against influenza in Poland in the epidemic season 1997/98. Patients and Methods: The study was carried out in 34 HIV-infected patients in different stages of the disease, vaccinated with a single 0.5ml dose of subunit vaccine ('Influvac', Solvay Pharmaceuticals BV). Antihaemagglutinin (HI) antibody levels were measured by the haemagglutinin inhibition test before immunisation and then after one and six months. Results: One month after Vaccination HI antibody titres significantly increased from 1.5 to 5.5 times. After six months HI antibody levels were higher than those before vaccination and also higher than those determined one month after vaccination. Before immunisation the number of patients with HI antibody titres greater than or equal to 1:40 ranged from 2.9 to 50%. After vaccination, protection rates increased and ranged from 17.6 to 79.4% one month after vaccination, and from 20.6 to 82.4% six months after vaccination. Response rate values remained at similar levels during the whole study and were between 9.4 and 14.7%. No statistically significant differences were found in humoral response between patients with different CD4 counts nor between AIDS patients and those not suffering from AIDS. Significantly higher antibody titres were recorded during the whole study for the A/Wuhan/359/95 (H3N2) influenza strain than for the A(H1N1) and B strains. Conclusions: The results of this study indicated that in HIV-infected patients humoral response to influenza vaccination was poor compared with healthy people. However, in some HIV-infected patients the vaccine induced the production of HI antibodies in titres that were considered high enough to protect against the infection.