Abstract
The advent of the 2009 H1N1 pandemic influenza has raised concerns about the immunogenicity and safety of vaccines against the new virus, especially in immunocompromised individuals. In our study we evaluated the immunogenicity and safety of pandemic influenza vaccine in 34 HIV-1 infected patients.
For immunization was used a single dose of adjuvanted inactivated split-virion pandemic H1N1 influenza vaccine containing 3.75 microg of hemagglutinin (A/California/7/2009) and adjuvant AS03. Two serum samples were collected from each patient - first on day 0 just before vaccination and the other on day 28 after vaccination.
Antibody production was tested by hemagglutinin inhibition assay according to the World Health Organization methodology. The mean baseline CD4+ T lymphocyte count was 511/microl (range 90-1151).
After vaccination, protective titers >=1:40 were found in 24 (70.5%) vaccinees and at least fourfold increase in antibody titers was detected in 27 vaccinees (79.4%). Seroconversion was not observed in 4 vaccinees (11.2%) whose antibody titers remained undetectable.
Subgroups with and without protective post-vaccination antibody titers differed in the proportion of patients with baseline HIV RNA viral load < 20 copies/ml (p=0.022). No serious adverse event was observed among the vaccinees, only nine individuals (26.5%) reported moderate pain at the application site lasting maximally two days.
The protection rate after vaccination of HIV-1 infected individuals with a single dose of studied pandemic H1N1 influenza vaccine, albeit low if compared with normal population, met the criteria set by European Committee for Medicinal Products for minimal immunogenicity.