The titers of preF-specific serum antibodies IgG1 and IgG2a induced by rChAd63-mDS-Cav1 were not statistically different, and the IgG2a/IgG1 ratio was close to 1, indicating that rChAd63-mDS-Cav1 stimulated balanced or mixed Th1/Th2 immune responses beneficial to avoid the enhanced respiratory disease (ERD) following the vaccination of FI-RSV. This evidence concerns the gene CAV1 and respiratory system disorder.