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

Author(s): 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

Journal: Revista de Saúde Pública
ISSN 0034-8910

Volume: 38;
Issue: 5;
Start page: 671;
Date: 2004;
Original page

Keywords: Yellow fever vaccine | Randomized controlled trials

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.
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Tango Jona
Tangokurs Rapperswil-Jona