OBJECTIVETo assess the antibody response to influenza vaccine of children vertically infected with HIV.
DESIGNProspective study in HIV infected children vaccinated during the winter of 1994-5.
SETTINGFamily HIV clinic at St Mary's Hospital, Paddington.
SUBJECTS25 children, aged 1-11 years, vertically infected with HIV.
MAIN OUTCOME MEASURESResponses to influenza antigens (H1N1-A /Taiwan /1/86, H3N2-A /Shandong /9/93, B /Panama /45/90) were tested by haemagglutination inhibition. Antibody responses were assessed according to clinical symptoms and immune function, stratified according to the 1994 revised classification for HIV infection in children.
RESULTS23 children (92%) had either very low or no detectable antibody before vaccination. New protective antibody responses were made by 10 children (40%): in seven to a single antigen, in two to two antigens, and in one to all three antigens. For each antigen there was an overall small increase in the mean geometric titre of antibody produced, but this only reached a protective level for antigen H1N1 and for children with minimal symptoms. Less symptomatic children were significantly more likely to produce a protective antibody response to influenza vaccination. No association was found between immune function, as measured by CD4 count, and vaccine response.
CONCLUSIONSOnly vaccination of the least symptomatic HIV infected children against influenza is likely to be effective. This will not only protect them against influenza, but will also protect other more immunosuppressed and vulnerable members of their families.

Keywords: influenza vaccination; paediatric HIV infection.