title: Protective efficacy of a trivalent recombinant hemagglutinin protein vaccine (FluBlok®) against influenza in healthy adults: a randomized, placebo-controlled trial.
abstract: BACKGROUND
  Development of influenza vaccines that do not use embryonated eggs as the substrate for vaccine production is a high priority. We conducted this study to determine the protective efficacy a recombinant, baculovirus-expressed seasonal trivalent influenza virus hemagglutinin (rHA0) vaccine (FluBlok(®)).
  
  
  METHODS
  Healthy adult subjects at 24 centers across the US were randomly assigned to receive a single injection of saline placebo (2304 subjects), or trivalent FluBlok containing 45 mcg of each rHA0 component (2344 subjects). Serum samples for assessment of immune responses by hemagglutination-inhibition (HAI) were taken from a subset of subjects before and 28 days after immunization. Subjects were followed during the 2007-2008 influenza season and combined nasal and throat swabs for virus isolation were obtained from subjects reporting influenza-like illness.
  
  
  RESULTS
  Rates of local and systemic side effects were low, and the rates of systemic side effects were similar in the vaccine and placebo groups. HAI antibody responses were seen in 78%, 81%, and 52% of FluBlok recipients to the H1, H3, and B components, respectively. FluBlok was 44.6% (95% CI, 18.8%, 62.6%) effective in preventing culture-confirmed influenza meeting the CDC influenza-like illness case definition despite significant antigenic mismatch between the vaccine antigens and circulating viruses.
  
  
  CONCLUSIONS
  Trivalent rHA0 vaccine was safe, immunogenic and effective in the prevention of culture confirmed influenza illness, including protection against drift variants.
authors.affiliation: University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA. John Treanor@urmc.rochester.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Treanor
authors.forename: Hana
authors.initials: H
authors.lastname: El Sahly
authors.forename: James
authors.initials: J
authors.lastname: King
authors.forename: Irene
authors.initials: I
authors.lastname: Graham
authors.forename: Ruvim
authors.initials: R
authors.lastname: Izikson
authors.forename: Robert
authors.initials: R
authors.lastname: Kohberger
authors.forename: Peter
authors.initials: P
authors.lastname: Patriarca
authors.forename: Manon
authors.initials: M
authors.lastname: Cox
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009666:Nose / Q000821:virology; D009975:Orthomyxoviridae / Q000302:isolation & purification; D010614:Pharynx / Q000821:virology; D010919:Placebos / Q000008:administration & dosage; D014481:United States; D014611:Vaccination / Q000379:methods; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; C528512:FluBlok; D007252:Influenza Vaccines; D010919:Placebos