Immunogenicity of WHO-17D and Brazilian 17DD yellow fever vaccines: a randomized trial

• Main Authors: Camacho Luiz Antonio Bastos, Freire Marcos da Silva, Leal Maria da Luz Fernandes, Aguiar Savitri Gomes de, Nascimento Jussara Pereira do, Iguchi Takumi, Lozana José de Azevedo, Farias Roberto Henrique Guedes
• Format: Article
• Language: English
• Published: Universidade de São Paulo 2004-01-01
• Series: Revista de Saúde Pública
• Subjects: Yellow fever vaccine; Randomized controlled trials
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0034-89102004000500009

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.