Antibody response of healthy children to pandemic A/H1N1/2009 influenza virus

Susanna Esposito, Cristina Daleno, Claudia Tagliabue, Alessia Scala, Irene Picciolli, Francesca Taroni, Carlotta Galeone, Fausto Baldanti, Nicola Principi

Research output: Contribution to journalArticlepeer-review


Background: Little is known about the proportion of pediatric pandemic A/H1N1/2009 influenza cases who showed seroconversion, the magnitude of this seroconversion, or the factors that can affect the antibody level evoked by the pandemic A/H1N1/2009 influenza. Aims of this study were to analyse antibody responses and the factors associated with high antibody titres in a cohort of children with naturally acquired A/H1N1/2009 influenza infection confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR). Results: Demographic, clinical and virologic data were collected from 69 otherwise healthy children with pandemic A/H1N1/2009 influenza (27 females, mean age SD: 5.01 4.55 years). Their antibody levels against pandemic A/H1N1/2009 and seasonal A/H1N1 influenza viruses were evaluated by measuring hemagglutination-inhibiting antibodies using standard assays. Sixty-four patients (92.8%) with pandemic A/H1N1/2009 influenza had A/H1N1/2009 antibody levels of 40, whereas only 28/69 (40.6%) were seroprotected against seasonal A/H1N1 influenza virus. Those who were seroprotected against seasonal A/H1N1 virus were significantly older, significantly more often hospitalised, had a diagnosis of pneumonia significantly more frequently, and were significantly more often treated with oseltamivir than those who were not seroprotected (p <0.05). The children with the most severe disease (assessed on the basis of a need for hospitalisation and a diagnosis of pneumonia) had the highest antibody response against pandemic A/H1N1/2009 influenza virus. Conclusions: Otherwise healthy children seem to show seroprotective antibody titres after natural infection with pandemic A/H1N1/2009 influenza virus. The strength of the immune response seems to be related to the severity of the disease, but not to previous seasonal A/H1N1 influenza immunity.

Original languageEnglish
Article number563
JournalVirology Journal
Publication statusPublished - 2011


  • Children
  • Immune response
  • Influenza
  • Pandemic A/H1N1/2009 influenza virus
  • Pediatric infectious diseases

ASJC Scopus subject areas

  • Virology
  • Infectious Diseases


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