How successful is influenza vaccination in HIV infected patients? Results from an influenza A(H1N1)pdm09 vaccine study

Aim: To determine immune response after single vaccination with AS03-adjuvanted pandemic H1N1 vaccine in HIV-infected patients.

Background: Individuals living with human immunodeficiency virus (HIV) are at risk with influenza due to hyporesponsiveness to influenza vaccine and a higher probability for developing severe disease. Especially, immunogenicity and tolerability of adjuvanted influenza vaccines in a pandemic setting are not well characterized in HIV infected individuals.

Methods: Immune response following vaccination with a single dose of influenza A (H1N1)pdm09 AS03- adjuvanted vaccine (H1N1pdm09 vaccine) containing 3.75 mg hemagglutinin was evaluated in HIV infected individuals by hemagglutination inhibition assay. Tolerability was assessed by questionnaires.

Results: Three hundred eighty-nine patients from two German HIV clinics were evaluated. Seroprotec- tion was found in as much as 191/389 (49%) of patients before vaccination. Following vaccination with H1N1pdm09 vaccine seroprotection rate increased to 66% (257/389). Due to high pre-vaccination seroprotection rates seroconversion was only found in a total of 27/389 (7%) of HIV patients. There was no association of seroprotection/seroconversion and current CD4+ T-cell count, HIV-RNA load in plasma, antiretroviral treatment or demographic factors such as gender, age and ethnicity. The vaccine was overall well tolerated.

Conclusions: In this large cohort of HIV infected patients with high baseline H1N1 seroprotective titers only a moderate antibody response to a single vaccination with H1N1pdm09 AS03-adjuvanted vaccine was detected. Emerging influenza pandemics warrant usage of booster vaccinations in order to achieve higher immunogenicity to protect a vulnerable patient population such as HIV positive individuals against influenza.