Efficacy and safety of intradermal vaccination against porcine circovirus type 2 and Mycoplasma hyopneumoniae under combined exposure field conditions

Background: Porcine circovirus 2 (PCV2) and Mycoplasma hyopneumoniae (M hyo) are two of the most important swine pathogens with variable clinical presence in swine farms globally, affecting health and performance of pigs under field conditions. The primary objective of this study was to assess the efficacy of a ready to use intradermal (ID) vaccine (Porcilis PCV M Hyo ID, MSD Animal Health, The Netherlands) against PCV2 associated disease and M hyo associated enzootic pneumonia under practical (field) conditions. In addition, the safety of the test product was clinically assessed, as the study animals were examined for general and local side effects after vaccination. A total of 678 animals in a Greek farrow to finish farm were equally divided in two trial groups (test and control group). Test group animals received the test vaccine at the age of three weeks, while control group animals remained unvaccinated. Parameters regarding health [lung lesion score (LLS) and pleurisy scoring, PCV2 viraemia and shedding] and performance [body weight (BW), average daily weight gain (ADWG)] were recorded and evaluated. Results: Vaccination improved the ADWG during both the finishing period (improvement by 34 g; p < 0.0001), and the overall period (increase by 24 g; p < 0.0001). Moreover, reduced mean LLS values (p < 0.0001), as well as reduced percentage of animals with pleurisy (p = 0.0082) and a decrease in PCV2 viraemia (p < 0.0001) and viral shedding (p = 0.0181) were observed in vaccinated animals when compared with the unvaccinated controls. As regards safety, a slight local skin reaction at the site of vaccination was detected and in two pigs a mild systemic reaction was reported with full recovery. Conclusions: Findings suggested that the test vaccine is safe and effective against both PCV2 and M hyo associated diseases in vivo, thus it’s use as part of a vaccination programme under field conditions is expected to improve respective health and performance parameters in pigs. © The Author(s) 2025.