Figure 1. Vaccine induced protection against leukopenia.

Leucokyte numbers remained at pre-vaccination levels throughout the experiment in animals vaccinated five days prior to challenge with A) UK2000/7.1 or B) CBR/93 (filled circles), whereas a significant (P<0.05) decrease occurred rapidly after challenge in unvaccinated animals (open circles) and animals vaccinated one day before challenge that developed clinical signs and were euthanized prior to the end of the experiment (open triangles). A smaller, non significant, decrease in leukocyte numbers was observed in animals vaccinated one day prior to challenge that did not develop clinical signs (filled triangles) and those vaccinated three days prior to challenge (filled squares). n = number of animals in groups vaccinated on day prior to challenge that either developed signs and were euthanized or remained clinically healthy. Data are mean leukocyte counts for each group of pigs. Error bars represent SEM.