Porcine Reproductive and Respiratory Syndrome Virus Infection at the Time of Porcine Circovirus Type 2 Vaccination Has No Impact on Vaccine Efficacy

Several porcine circovirus type 2 (PCV2) vaccines are now commercially available and have been shown to be effective at decreasing the occurrence of porcine circovirus-associated disease (PCVAD). Many herds are coinfected with PCV2 and porcine reproductive and respiratory syndrome virus (PRRSV). Some producers and veterinarians are concerned that if pigs are vaccinated for PCV2 at or near the time that they are typically infected with PRRSV, the efficacy of the PCV2 vaccine will be compromised. The impact of PRRSV on PCV2 vaccination is unclear and has not been investigated under controlled conditions. The objective of the present study was to determine whether the presence of PRRSV viremia has an effect on the efficacy of commercial PCV2 vaccinations. Three-week-old PCV2-negative conventional pigs with passively derived anti-PCV2 antibodies were either vaccinated with one of three commercial PCV2 vaccines or left nonvaccinated. A portion of the pigs were infected with PRRSV 1 week prior to PCV2 vaccination. To determine vaccine efficacy, a PCV2 challenge was conducted at 8 weeks of age. PCV2 vaccination, regardless of PRRSV infection status at the time of vaccination, was similarly effective in inducing an anti-PCV2 IgG response in the presence of maternally derived immunity and in protecting the pigs from PCV2 challenge, as determined by a reduction in the level of PCV2 viremia and a reduction in the prevalence and amount of PCV2 antigen in lymphoid tissues in vaccinated pigs compared to nonvaccinated pigs. The results indicate that acute PRRSV infection at the time of PCV2 vaccination has no adverse effect on PCV2 vaccine efficacy.