FIG. 3.

Influence of vaccine type on the presence or absence of virus in nose and throat samples taken on days 3, 5, and 7 postchallenge with homologous clade A/Vietnam/1203/04 virus. The data are combined from the different experiments described in the present study that included ferrets immunized with the indicated vaccines or PBS control animals. Nasal washings and also oral swabs taken into PBS were sampled on the indicated days postchallenge and tested for the presence of infectious virus by amplification in eggs. The data indicate the fraction of ferrets: red square, virus present in nasal and/or throat samples; white square, no virus detected in either nasal or throat samples; black square, animal previously culled. Statistical analyses of the vaccine groups compared to the control group for the relevant day postinfection were performed using the Fisher exact test with 95% confidence levels. The P values for those groups that were significantly different from the control group are shown as asterisks below the group, the number of stars indicates the P value as defined at the bottom of the figure. NS, not significantly different. No indicator, statistics unable to be performed as all shedding virus (therefore not different).