Fig. 2.

Anti-comet test. After BS-C-1 cells were infected with the IHD strain of vaccinia virus, pooled serum diluted 1:50 from mice immunized twice with MVA (10⁶ to 10⁸ pfu) or once with Dryvax was added to the liquid overlay medium. After 48 h, the monolayers were stained with crystal violet.