Figure 3

Mean serum antibody levels (A ₄₅₀ ) to Actinobacillus pleuropneumoniae serotype 2 in batches of pigs vaccinated two or three times against Actinobacillus pleuropneumoniae in a specialized fattening herd affected by the infection. The first vaccination was performed as the pigs arrived at the specialized fattening herd. The booster vaccination(s) were carried out after intervals of 28 days, Double vaccinated pigs are shown by filled symbols ([black diamond] = batch 8 and [black circle] = batch 10. Pigs vaccinated three times are shown by open symbols (black triangle = batch 1 and black sqaure = batch 8). The dotted line indicates the cut-off value for a positive reaction.