title: Cell culture (Vero cell) derived whole-virus non-adjuvanted H5N1 influenza vaccine induces long-lasting cross-reactive memory immune response: homologous or heterologous booster response following two dose or single dose priming.
abstract: BACKGROUND
  Influenza pandemic preparedness involves priming of the population with pre-pandemic vaccines. Such vaccines should be well tolerated and induce a long-lasting immunological memory that can effectively be boosted with a single dose of pandemic vaccine once available. The presented studies assessed different prime-boost regimens with a Vero cell-derived whole virus non-adjuvanted H5N1 vaccine.
  
  
  METHODS
  In one study, 281 healthy adult (18-59 years) and 280 elderly (≥ 60 years) subjects received two vaccinations, 21 days apart, with Vero cell-derived whole virus non-adjuvanted H5N1 vaccine (7.5 μg HA Antigen A/Vietnam/1203/2004) followed by a 6, 12-15, or 24 month booster (7.5 or 3.75μg A/Indonesia/05/2005 or A/Vietnam/1203/2004). In the other study, 230 healthy adults (18-59 years) received single dose priming (7.5 μg A/Vietnam/1203/2004) followed by a 12 month booster (7.5 or 3.75 μg A/Indonesia/05/2005). Antibody responses were assessed by microneutralization (MN) and single radial hemolysis (SRH) assay. Vaccine safety was assessed throughout.
  
  
  RESULTS
  Two dose priming was equally immunogenic in adults and the elderly: >72% of subjects in each population achieved MN titers ≥ 1:20 after the second vaccination. Booster vaccinations at 6, 12-15, and 24 months induced substantial antibody increases to both strains: after a 7.5 μg A/Indonesia/05/2005 booster, 93-95% of adults and 72-84% of the elderly achieved MN titers ≥ 1:20 against this strain. Homologous and heterologous booster responses were higher in the 7.5μg dose group than in the 3.75 μg dose group. Booster responses following single dose priming were similar; a 7.5 μg booster dose induced homologous MN titers ≥ 1:20 in 93% of subjects.
  
  
  CONCLUSIONS
  A Vero cell derived whole virus non-adjuvanted H5N1 influenza vaccine is well tolerated and induces long-lasting cross-clade immunological memory that can be effectively boosted 1-2 years after two dose or single dose priming, supporting its suitability for pre-pandemic vaccination.
authors.affiliation: Vaccine R&D, Baxter BioScience, Vienna, Austria.
authors.forename: Maikel V W
authors.initials: MV
authors.lastname: van der Velden
authors.forename: Gerald
authors.initials: G
authors.lastname: Aichinger
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Pöllabauer
authors.forename: Alexandra
authors.initials: A
authors.lastname: Löw-Baselli
authors.forename: Sandor
authors.initials: S
authors.lastname: Fritsch
authors.forename: Karima
authors.initials: K
authors.lastname: Benamara
authors.forename: Otfried
authors.initials: O
authors.lastname: Kistner
authors.forename: Markus
authors.initials: M
authors.lastname: Müller
authors.forename: Markus
authors.initials: M
authors.lastname: Zeitlinger
authors.forename: Herwig
authors.initials: H
authors.lastname: Kollaritsch
authors.forename: Timo
authors.initials: T
authors.lastname: Vesikari
authors.forename: Hartmut J
authors.initials: HJ
authors.lastname: Ehrlich
authors.forename: P Noel
authors.initials: PN
authors.lastname: Barrett
mesh_terms: D000328:Adult; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D002522:Chlorocebus aethiops; D003429:Cross Reactions / Q000276:immunology*; D005260:Female; D006801:Humans; D007117:Immunization, Secondary; D007156:Immunologic Memory; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D014709:Vero Cells; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines