RESUMO
BACKGROUND: A phase 2 trial was conducted to assess in young infants the safety, tolerability, infectivity, and immunogenicity of multiple doses of an intranasal vaccine using bovine parainfluenza virus type 3 (bPIV3). METHODS: One hundred ninety-two healthy 2-month-old infants were randomized 1 : 1 : 1 to receive 1x10(5) median tissue culture infective dose (TCID(50)) bPIV3 vaccine, 1x10(6) TCID(50) bPIV3 vaccine, or placebo at 2, 4, 6, and 12-15 months of age. Safety information was collected by use of diary sheets and telephone interviews. Nasal wash and serum specimens were collected for assessment of infectivity and immunogenicity. RESULTS: The safety profiles of both dosages of bPIV3 were similar to that of placebo, with the exception of fever with temperature of >/=38.1 degrees C after dose 2 only, occurring in 34% of the 1x10(5) TCID(50) group, 35% of the 1x10(6) TCID(50) group, and 12% of the placebo group (P<.01). No vaccine-related serious adverse events were reported. The cumulative vaccine infectivity (isolation of bPIV3 and/or bPIV3 seroconversion) after dose 3 was similar in the 2 vaccine groups (87% in the 1x10(5) TCID(50) group and 77% in the 1x10(6) TCID(50) group) (P=.46). Seroconversion rates after dose 3, assessed by means of hemagglutination inhibition assay, after adjustment for decrease in maternal antibody titers, were 67% in the 1x10(5) TCID(50) group, 57% in the 1x10(6) TCID(50) group, and 12% in the placebo group (P<.01). Isolation of bPIV3 was common after dose 1, dose 2, or dose 3, but only 1 of 51 participants in the vaccine groups had bPIV3 isolated after dose 4. CONCLUSIONS: Multiple doses of bPIV3 vaccine were well tolerated and immunogenic in young infants.
