title: Immunogenicity of WHO-17D and Brazilian 17DD yellow fever vaccines: a randomized trial.
abstract: OBJECTIVE
  To compare the immunogenicity of three yellow fever vaccines from WHO-17D and Brazilian 17DD substrains (different seed-lots).
  
  
  METHODS
  An equivalence trial was carried out involving 1,087 adults in Rio de Janeiro. Vaccines produced by Bio-Manguinhos, Fiocruz (Rio de Janeiro, Brazil) were administered following standardized procedures adapted to allow blocked randomized allocation of participants to coded vaccine types (double-blind). Neutralizing yellow fever antibody titters were compared in pre- and post-immunization serum samples. Equivalence was defined as a difference of no more than five percentage points in seroconversion rates, and ratio between Geometric Mean Titters (GMT) higher than 0.67.
  
  
  RESULTS
  Seroconversion rates were 98% or higher among subjects previously seronegative, and 90% or more of the total cohort of vaccinees, including those previously seropositive. Differences in seroconversion ranged from -0.05% to -3.02%. The intensity of the immune response was also very similar across vaccines: 14.5 to 18.6 IU/mL. GMT ratios ranged from 0.78 to 0.93. Taking the placebo group into account, the vaccines explained 93% of seroconversion. Viremia was detected in 2.7% of vaccinated subjects from Day 3 to Day 7.
  
  
  CONCLUSIONS
  The equivalent immunogenicity of yellow fever vaccines from the 17D and 17DD substrains was demonstrated for the first time in placebo-controlled double-blind randomized trial. The study completed the clinical validation process of a new vaccine seed-lot, provided evidence for use of alternative attenuated virus substrains in vaccine production for a major manufacturer, and for the utilization of the 17DD vaccine in other countries.
authors.affiliation: Escola Nacional de Saúde Pública, Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil. luiz.camacho@ensp.fiocruz.br
authors.forename: Luiz Antonio Bastos
authors.initials: LA
authors.lastname: Camacho
authors.forename: Marcos da Silva
authors.initials: Mda S
authors.lastname: Freire
authors.forename: Maria da Luz Fernandes
authors.initials: Mda L
authors.lastname: Leal
authors.forename: Savitri Gomes de
authors.initials: SG
authors.lastname: Aguiar
authors.forename: Jussara Pereira do
authors.initials: JP
authors.lastname: Nascimento
authors.forename: Takumi
authors.initials: T
authors.lastname: Iguchi
authors.forename: José de Azevedo
authors.initials: Jde A
authors.lastname: Lozana
authors.forename: Roberto Henrique Guedes
authors.initials: RH
authors.lastname: Farias
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D015004:Yellow Fever / Q000517:prevention & control; D022341:Yellow Fever Vaccine / Q000276:immunology*; D015005:Yellow fever virus / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D022341:Yellow Fever Vaccine