Early proliferation of antigen-specific CD8⁺ T cells occurs in spleen and lymph nodes following booster vaccination with B/VSV. Ad-GP33–primed (1 × 10⁸ PFU intramuscularly) C57BL/6 mice were boosted 14 days later with B/VSV-GP33 or B/VSV-MT as control. FTY 720 was given 2 hours before B/VSV delivery to block lymphocyte circulation. Each group received IP injection of BrdU 24 hours before tissue harvest, at which time BrdU⁺ GP33-specific CD8⁺ T cells were enumerated (n = 5/group/time point; *P < .01 compared with B/VSV-MT control). IFN, interferon.