Commercial PCV2 vaccines are remarkably effective in controlling PCVAD. However, there are still concerns regarding the appearance of what appears to be “vaccination failures”, which presumably result from high levels of maternal antibody or antibody produced by nursery pigs in response to natural infection. In this project, we evaluated the role of maternal antibody in blocking the vaccine response to the two-shot Intervet PCV2 vaccine (Circumvent). The study design included nearly equal numbers of vaccinated and non-vaccinated pigs. The end-point of effective vaccination was identified as increased body weight compared to non-vaccinated pigs (Horlen et al, 2008, JAVMA 232:906). The results showed no correlation between the level of maternal antibody present at the time of first vaccination and body weight. The analysis of approximately 900 serum samples using a PCV2 PCR showed no evidence of PCV2 infection in the nursery. The results from this study confirm the effectiveness of PCV2 vaccination, even in the face of maternal antibody. Furthermore, the data suggest that vaccine-induced antibody combined with maternally-derived antibody can provide effective protection from farrow through finish. Raymond R. R. Rowland, [email protected], 785-532-4631