Immunogenicity of the pentavalent rotavirus vaccine among infants in two developing countries in Asia, Bangladesh and Vietnam

ArticleinVaccine Supplement(1):A106–A113 · April 2012with13 Reads
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    Background: We evaluated the immunogenicity of the pentavalent rotavirus vaccine (PRV) in two GAVIeligible
    Asian countries, Bangladesh and Vietnam, nested in a larger randomized, double-blind, placebocontrolled
    efficacy trial conducted over a two-year period from 2007 through 2009.
    Methods: 2036 infants were randomly assigned, in a 1:1 ratio, to receive three oral doses of PRV or
    placebo approximately at 6, 10, and 14 weeks of age. Concomitant use of EPI vaccines, including oral
    poliovirus vaccine (OPV) and diphtheria-tetanus-whole cell pertussis (DTwP) vaccine, was encouraged
    in accordance to the local EPI schedule. A total of 303 infants were evaluated for immunogenicity and
    blood samples were collected before the first dose (pD1) and approximately 14 days following the third
    dose (PD3). The seroresponse rates (≥3-fold rise from pD1 to PD3) and geometric mean titers (GMTs)
    were measured for anti-rotavirus immunoglobulin A (IgA) and serum neutralizing antibody (SNA) to
    human rotavirus serotypes G1, G2, G3, G4, and P1A[8], respectively.
    Results: Nearly 88% of the subjects showed a
    ≥3-fold increase in serum anti-rotavirus IgA response in
    the analysis of the two countries combined. When analyzed separately, the IgA response was lower in
    Bangladeshi children (78.1% [95% CI: 66.0, 87.5]) than in Vietnamese children (97.0% [95% CI: 89.6, 99.6]),
    with a PD3 GMT of 29.1 (units/mL) and 158.5 (units/mL), respectively. In the combined population, the
    SNA responses to the individual serotypes tested ranged from 10 (G3) to 50 (G1) percentage points lower
    than the responses shown in the developed countries. However, the SNA response to G3 in Vietnamese
    subjects was 37.3% (95% CI: 25.8, 50.0), which was similar to the G3 response rate in developed countries.
    Conclusions: Three oral doses of PRV were immunogenic in two GAVI-eligible Asian countries: Bangladesh
    and Vietnam. The GMTs of both the serum anti-rotavirus IgA and SNA responses were generally higher
    in Vietnamese than in Bangladeshi children. The SNA responses varied by individual serotypes and were
    lower than the results from developed countries. The clinical significance of these observations is not
    understood because an immune correlate of protection has not been established.