FIG. 4.

Serum Ab responses after intranasal and intraperitoneal priming. Immunization groups are designated as described in Table 4. All immunizations were with inactivated influenza virus vaccine plus 0.1 μg of CT. Sera were collected 14 days after primary immunization. The results are from sera collected from three experiments. A single asterisk denotes statistical differences (P ≤ 0.05) from the value for the control, while double asterisks denote differences (P ≤ 0.05) from values for mice given primary immunizations only (0:IN and IP:0).