Influenza surveillance and vaccination in Hong Kong children
TF Leung1, PKS Chan2, KL Hon1, AM Li1, FWT Cheng1
1 Department of Paediatrics, The Chinese University of Hong Kong
2 Department of Microbiology, The Chinese University of Hong Kong
1. This prospective influenza surveillance study found that mild influenza infection was common among Hong Kong children aged 2 to 12 years during the influenza seasons of 2014-2015.
2. Seasonal influenza vaccination protected against influenza-like illness (ILI) but not laboratory-confirmed influenza in surveillance samples of local children. The effectiveness of influenza vaccine for ILI varied between 42.1% and 51.9%.
3. Seropositivity, defined by a haemagglutination inhibition titre of ≥1:40, was found in 92%, 91%, 68%, 49%, and 85% of participants for pandemic A/H1N1, A/H3N2, A/H3N2_Switzerland, B/Victoria, and B/Yamagata, respectively. However, neither haemagglutination inhibition titre nor seropositivity was a useful surrogate of influenza immunity in children.
4. Neither ILI nor influenza infection was associated with any demographic, environmental, or clinical factors in the children.
5. Approximately half of local preschool and primary school children had received seasonal influenza vaccination within the past 3 years.