Antibody responses to bovine parainfluenza virus type 3 (PIV3) vaccinationand human PIV3 infection in young infants

A phase 2 clinical trial was conducted to evaluate the antibody responses t o bovine parainfluenza virus type 3 (bPIV3) vaccination in young infants. T hree groups were tested as follows: placebo (n = 66) and 10(5) (n = 64) or 10(6) (n = 62) TCID50 of bPIV3. The vaccine or placebo was administered int ranasally at ages 2, 4, 6, and 12-15 months, and serum specimens were colle cted at ages 2, 6, 7, 12-15, and 13-16 months. Serum hemagglutination inhib ition (HI) and IgA antibody titers against bPIV3 and human PIV3 (hPIV3) wer e measured: The results indicate that antibody responses to bPIV3 vaccinati on are more likely to be detected by the bPIV3 IgA and HI assays than by th e hPIV3 IgA and HI assays, that bPIV3-induced antibody response can be diff erentiated from hPIV3-induced antibody response most reliably by comparing bPIV3 and hPIV3 HI titers, and that bPIV3 vaccine prevents vaccine recipien ts from developing antibody profiles of hPIV3 primary infection.