Absence of cross-reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months-9 years: a prospective study

Abstract

Please cite this paper as: McVernon et al. (2010) Absence of cross‐reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months–9 years: a prospective study. Influenza and Other Respiratory Viruses 5(1), 7–11. Background Early outbreaks of the pandemic influenza A (H1N1) 2009 virus predominantly involved young children, who fuelled transmission through spread in homes and schools. Seroprevalence studies conducted on stored serum collections indicated low levels of antibody to the novel strain in this age group, leading many to recommend priority immunisation of paediatric populations. Objectives In a prospective study, we sought evidence of cross‐reactive antibodies to the pandemic virus in children who were naïve to seasonal influenza vaccines, at baseline and following two doses of the 2009 Southern Hemisphere trivalent influenza vaccine (TIV). Patients/Methods Twenty children were recruited, with a median age of 4 years (interquartile range 3–5 years); all received two age appropriate doses of TIV. Paired sera were collected pre‐ and post‐vaccination for the assessment of vaccine immunogenicity, using haemagglutination inhibition and microneutralisation assays against vaccine‐related viruses and influenza A (H1N1) 2009. Results Robust responses to H3N2 were observed regardless of age or pre‐vaccination titre, with 100% seroconversion. Fewer seroconverted to the seasonal H1N1 component. Only two children were weakly seropositive (HI titre 40) to the pandemic H1N1 strain at study entry, and none showed evidence of seroconversion by HI assay following TIV administration. Conclusions Administration of 2009 Southern Hemisphere TIV did little to elicit cross‐reactive antibodies to the pandemic H1N1 virus in children, in keeping with assay results on stored sera from studies of previous seasonal vaccines. Our findings support the recommendations for influenza A (H1N1) 2009 vaccination of children in preparation for the 2010 winter season.

Multi-Dimensional Measurement of Antibody-Mediated Heterosubtypic Immunity to Influenza

“…Individuals with pre-existing HSI generally will have a strong memory B cell recall response to vaccination, and exhibit larger and more rapid antibody secretion response to vaccination with related influenza strains. The absence of preexisting HSI may result in a weaker response and less protective immunity [ 8 ]. As such, determining influenza vaccine efficacy requires that we know the pre-vaccine baseline pattern of HSI.…”

Sequential Seasonal H1N1 Influenza Virus Infections Protect Ferrets against Novel 2009 H1N1 Influenza Virus

“…oon after the novel H1N1 influenza outbreak in 2009, it became apparent that younger people and children were more susceptible to infection than older individuals (1)(2)(3)(4)(5). Serological studies revealed that many older and middle-aged adults possessed antibodies that reacted with the novel H1N1 virus prior to the pandemic (6,7).…”

Complex Patterns of Human Antisera Reactivity to Novel 2009 H1N1 and Historical H1N1 Influenza Strains

“…In April 2009, the first cases of novel influenza H1N1 were identified in North America. Our group and others demonstrated that of the ∼65 million people that were infected in the United States by the end of 2009, infection and disease were highest in school-age children, and severe cases were underrepresented in elderly adults [5] , [6] , [7] , [8] , [9] . Structural analysis of the HA shows a conservation within antigenic regions of 1918 and 2009 pandemic HA proteins that is not present in contemporary seasonal H1N1 viruses [10] , [11] .…”