Low Immunogenicity of the 2009 Influenza A (H1N1) Vaccine in HIV-Infected Patients

The CDC recommends yearly influenza vaccination for all HIV-infected persons. However, the immunogenicity of influenza vaccines in this population appears to be somewhat variable.

Researchers recently examined immune responses to the 2009 influenza A (H1N1) vaccine among 120 HIV-infected patients aged 40 to 53 in Philadelphia. All patients except one were receiving antiretroviral therapy, and 92% had HIV viral loads <400 copies/mL. The median CD4 count was 502 cells/mm³; the median nadir count was 131 cells/mm³.

Participants received a single intramuscular 15-μg injection of the monovalent, inactivated, split-virus H1N1 influenza vaccine (Novartis). Blood samples were collected at baseline and 21 to 28 days after vaccination for determination…