A 1-year follow-on study from a randomised, head-to-head, multicentre, open-label study of two pandemic influenza vaccines in children

Hemagglutination inhibiting antibody persistence 1 year after influenza vaccination in Korean children and adolescents

This study aimed to assess the 1-y immunogenicity of influenza vaccines and the association between immunogenicity at 1 m and further influenza infections in children aged 6 m to 18 y. Serum hemagglutination inhibition (HI) antibody titers and GMTs were determined for the recommended influenza strains 0, 1, 6, and 12 m post-vaccination. The serological evidence of influenza infections were defined as the increase of HI titer (HI ≥1:40 and 4-fold rise). The seroprotection rates for strains A(H1N1), A(H3N2), and B were 91.2%, 87.6%, and 87.6%, respectively, at 1 month (n = 174). These rates were 76.5%, 64.7%, and 54.6%, respectively, at 12 m. The seroprotection rates and GMTs for influenza A(H1N1) and A(H3N2) were higher at 12 m than at 0 m (p < 0.05) but not for B. There were 39 subjects (42 cases) of serological influenza infections. Subjects with seroprotection at 1 m post-vaccination had showed fewer serologic A(H1N1) (10.1 vs 54.5%) and A(H3N2) (7.2 vs 38.1%) infections than the ones with HI titer <1:40 during follow-up (P < 0.01). In conclusion, influenza vaccines used during the 2008-09 season induced adequate 1-y immunogenicity for A(H1N1) and A(H3N2). The immunogenicity at one month after vaccination influenced further serological influenza infections.

Pandemic influenza A (H1N1) 2009 vaccination in children: a UK perspective

Pandemic H1N1 influenza infection was common in the UK in 2009 and children were particularly vulnerable. Most cases were mild or subclinical, but there was significant mortality, predominantly in those with pre-existing disease. Despite the rapid development of monovalent pandemic vaccines, and the fast-tracked approval process, these products were not available for large-scale use until the end of the second wave of infection. Vaccine uptake was relatively low, both among children and health-care workers. The monovalent pandemic vaccines and the 2010/2011 trivalent seasonal influenza vaccines were immunogenic and effective, and they probably reduced the impact of the third wave of infection. Vaccines containing novel adjuvants enabled antigen sparing, but safety concerns could limit the future use of these adjuvanted influenza vaccines in children. Public perceptions that the threat of the pandemic was exaggerated by the authorities, and concerns about vaccine safety, might prompt an inadequate response to the next influenza pandemic, potentially compromising public health.