Measurement of mucosal anti-HA specific IgA antibody levels by indirect ELISA. Groups of mice (n = 6) were orally vaccinated three times on days 0, 7, and 21 with 200 μl containing inactivated or live recombinant baculovirus at a log2 HA titer of 8, adjuvanted with or without 10 μg rCTB. Each point represents the arithmetic mean value (n = 6) ± SD (*, P < 0.05; **, P < 0.02; ***, P < 0.001).