The efficacy of a live chimeric porcine circovirus (PCV) type 1-2 vaccine based on subtype PCV2a was evaluated in a PCV2b and porcine reproductive and respiratory syndrome virus (PRRSV) coinfection model. Eighty-three, 2-week-old pigs were randomized into 12 treatment groups including eight vaccinated and four control groups. Pigs were vaccinated intramuscularly or orally at 3 weeks of age followed by inoculation with PCV2b and PRRSV at 7 weeks of age. PCV1-2a vaccination elicited an anti-PCV2-IgG response which was delayed in pigs vaccinated orally. Intramuscular vaccination significantly reduced PCV2b viremia compared to non-vaccinated pigs. The results indicate that PCV1-2a vaccination induced protective immunity against PCV2 in pigs experimentally coinfected with PCV2b and PRRSV and the intramuscular route of vaccination is more effective than oral.