Long-term seroprotective response of trivalent seasonal influenza vaccine in HIV-infected children, regardless of immunogenicity before immunisation.

Influenza vaccination can reduce disease in HIV-infected children. The durability of the antibody response after trivalent influenza vaccine is important for management. The aim of this prospective study was to assess the durability of seroprotection for trivalent influenza vaccine strains and the factors effecting seroprotective response regardless of immunogenicity before trivalent influenza vaccine at one and six months after immunisation. Hemagglutination inhibition assay was done at one and six months. Seventy-five HIV-infected children were enrolled after vaccination. Four children were lost to follow-up. None of the children had confirmed influenza infection between immunisation and hemagglutination inhibition at six months after influenza vaccination. Seventy-one children were included in the final analysis and immunogenicity of trivalent influenza vaccine strains at one and six months. Of these, 27 (38%) had complete seroprotection (Group A) and 44 (62%) had non-complete seroprotection (Group B). Sex, age and the body mass index of both groups were not different from each other (p > 0.05). There was a higher mean CD4 level and more children with RNA ≤40 copies/mL among Group A compared with Group B (p < 0.05). Other factors did not differ significantly. The durability of the seroprotective response after trivalent influenza vaccine was associated with a high CD4 level and virological suppression before vaccination.