Fig. 4.

Box plot showing the opsonophagocytic activity (OPA) of sera before and after the fifth dose. OPA is measured as the titer of respiratory burst as described in Materials and Methods. A single measurement using serial 2-fold dilutions of serum was examined; n=80 and 75 in pre- and postvaccination groups, respectively. The bubble plot shows the OPA distribution of the 75 paired pre- and postvaccination sera. The bubble size correlates to the number of paired sera with identical titers before and after vaccination.