A field study was conducted to investigate the effect of vaccination against porcine circovirus type 2 (PCV2) in pigs suffering from porcine respiratory disease complex (PRDC). A total of 1542 pigs were allocated randomly into two treatment groups at approximately 20 days of age. Groups received either a Baculovirus-expressed recombinant PCV2 Open Reading Frame (ORF) 2 vaccine or placebo by single intramuscular injection. Median onset of PCV2 viraemia and respiratory signs occurred when animals were 18 weeks old. Vaccination reduced the mean PCV2 viral load by 55-83% (p < 0.0001) and the mean duration of viraemia by 50% (p < 0.0001). During the period of study (from 3 to 25 weeks of age) vaccinated animals exhibited a reduced mortality rate (6.63% vs. 8.67%, difference -2.04%; p = 0.1507), an improved average daily weight gain (649 g/day vs. 667 g/day; difference +18 g/day; p < 0.0001) and a reduced time to market (164.8 days vs. 170.4 days; difference -5.6 days; p < 0.0001). The effects on performance were greatest in the 8-week period between the onset of PCV2 viraemia and the end of finishing. These data demonstrate that vaccination against PCV2 alone can significantly improve the overall growth performance of pigs in a multi-factorial, late occurring disease complex such as PRDC.