title: Antibody responses to natural influenza A/H1N1/09 disease or following immunization with adjuvanted vaccines, in immunocompetent and immunocompromised children.
abstract: OBJECTIVE
  To compare antibody responses elicited by influenza A/H1N1/09 disease and immunization with adjuvanted vaccines, in immunocompetent or immunocompromised children.
  
  
  METHODS
  Prospective parallel cohort field study enrolling children with confirmed influenza A/H1N1/09 disease or immunized with 1 (immunocompetent) or 2 (immunocompromised) doses of influenza A/H1N1/09 squalene-based AS03- or MF59-adjuvanted vaccines. Antibody geometric mean titers (GMT) were measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays 4-6 weeks after vaccination/disease. Vaccine adverse events were self-recorded in a 7-day diary.
  
  
  RESULTS
  Antibody titers were as high in 48 immunocompetent children after a single immunization (HAI and MN seroprotection rates: 98%; HAI-GMT: 395, MN-GMT: 370) as in 51 convalescent children (seroprotection rates: 98% (HAI) and 92% (MN); GMT: 350 (HAI) and 212 (MN). Twenty-seven immunocompromised children reached slightly lower seroprotection rates (HAI: 89%, MN: 85%) but similar antibody titers (HAI-GMT: 306, MN-GMT: 225) after 2 immunizations. Adverse events increased with age (P=0.01) and were more frequent with Pandemrix® than Focetria® (P=0.03).
  
  
  CONCLUSIONS
  Similarly high seroresponses may be expected in immunocompetent children after a single dose of adjuvanted vaccines as responses of convalescent children. Two vaccine doses were sufficient for most immunocompromised children.
  
  
  BACKGROUND
  NCT0102293 and NCT01022905.
authors.affiliation: Center for Vaccinology and Neonatal Immunology, Department of Pediatrics and Pathology-Immunology, University Hospitals of Geneva & Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Sara
authors.initials: S
authors.lastname: Meier
authors.forename: Michael
authors.initials: M
authors.lastname: Bel
authors.forename: Arnaud
authors.initials: A
authors.lastname: L'huillier
authors.forename: Pierre-Alex
authors.initials: PA
authors.lastname: Crisinel
authors.forename: Christophe
authors.initials: C
authors.lastname: Combescure
authors.forename: Laurent
authors.initials: L
authors.lastname: Kaiser
authors.forename: Stéphane
authors.initials: S
authors.lastname: Grillet
authors.forename: Klara
authors.initials: K
authors.lastname: Pósfay-Barbe
authors.forename: Claire-Anne
authors.initials: CA
authors.lastname: Siegrist
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000009:adverse effects; D000293:Adolescent; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D002648:Child; D002675:Child, Preschool; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007114:Immunization; D016867:Immunocompromised Host; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology* / Q000517:prevention & control; D008297:Male; D009500:Neutralization Tests; D011446:Prospective Studies; D013185:Squalene / Q000008:administration & dosage
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D007252:Influenza Vaccines; C558220:focetria; C556153:pandemrix; D013185:Squalene