FIG. 3.

Subjects with enhanced bactericidal activity after immunization with acellular pertussis vaccine. Relative survival was determined as described in the legend to Fig. 2. Values were compared using the Student t test. Asterisks denote statistically significant differences (P < 0.05) for the pre- and postimmunization values indicated by the vertical arrows. A dagger denotes a statistically significant difference (P < 0.05) for the dilutions of postimmunization values indicated by the horizontal arrow.