Antibody persistence and response to 2010-2011 trivalent influenza vaccine one year after a single dose of 2009 AS03-adjuvanted pandemic H1N1 vaccine in children

Background: In 2009, several countries used the AS03-adjuvanted pandemicA/H1N1 vaccine. We assessed the persistence of antibody and the priming induced by a single paediatric dose of this vaccine in children. Methods: Children aged 15-120 months vaccinated one year before with the AS03-adjuvanted monovalent pandemic vaccine were tested for the presence of antibody against 2010-2011 TIV components (A/California/7/2009(H1N1), A/Wisconsin/15/2009 (H3N2 A/Perth/16/2009-like) and B/Brisbane/60/2008) before and 21-28 days after each dose of 2010-2011 TIV. Hemagglutination-inhibition (HAI) assay was used. Children received one or two doses of 2010-2011 TIV at 21-28 days interval in relation with their previous immunization status. Results: The results of 128 children were included in the ATP analysis. Before the 2010-2011 TIV administration, 46% of children showed sero-protection to the A/California/7/2009(H1N1) strain (HAI titre >= 40) with lower rates of sero-protection to the H3N2A/Perth/16/2009 (37%) and B/Brisbane/60/2008 (19%). After the first dose of 2010-2011 TIV, 98%, 75%, and 57% of vaccinees attained a sero-protective titre to A/California/7/2009(H1N1), A/Perth/16/2009(H3N2), and B/Brisbane/60/2008 strain, respectively. The youngest age group showed significantly lower antibody response to the influenza B component compared to the older age groups after the first dose of vaccine. Among vaccinees who received the second dose of TIV, 96% and 87% had a sero-protective titre to H3N2A/Perth/16/2009 and B/Brisbane/60/2008, respectively. The 2010-2011 TIV was well tolerated. Conclusions: We found substantial persistence of antibody to the A/California/7/2009 strain one year after a single paediatric dose of AS03-adjuvanted pandemic vaccine and a seroprotective level of antibody to this strain in virtually all children who received one year later a single dose of the 2010-2011 TIV. In contrast, two doses of the 2010-2011 TIV were necessary to induce an adequate immune response to the A/Perth/16/2009(H3N2) and B/Brisbane/60/2008 strains in children previously naive to seasonal vaccine. (C) 2011 Elsevier Ltd. All rights reserved.