Growth performance equivalence of three commercial PCV2 vaccination strategies under shared natural exposure: A...

Despite the widespread use of porcine circovirus type 2 (PCV2) vaccines in commercial swine production, evidence from randomized comparative field studies conducted under routine commercial production conditions remains limited. We conducted a prospective, randomized, blinded, parallel-group equivalence trial to evaluate whether a PCV2b whole-virus inactivated vaccine could achieve growth performance equivalent to that of two established commercial PCV2 vaccines under shared natural exposure. A total of 309 piglets were randomly allocated to three vaccination groups at 27 days of age and commingled throughout the study to minimize differences in management and infection pressure. Average daily gain (ADG) from 27 to 158 days of age was predefined as the primary endpoint and evaluated using a prespecified equivalence margin of ±35 g/day. Secondary outcomes included safety, mortality, morbidity, treatment burden, and longitudinal virological and serological responses. Following prespecified exclusions, 73, 77, and 75 pigs remained in Groups A, B, and C, respectively, for the primary analysis. The ANCOVA-adjusted difference was 6.2 g/day for Group A versus Group B (90% CI, -14.1-26.6) and -11.3 g/day for Group A versus Group C (90% CI, -31.7-9.2); both confidence intervals were entirely contained within the prespecified equivalence margin. No statistically significant between-group differences were detected in mortality, morbidity, treatment burden, or longitudinal PCV2 viremia. Serological responses differed at selected time points, but these differences were not accompanied by corresponding differences in growth, clinical, or virological outcomes. These findings demonstrate equivalent growth performance between the evaluated PCV2b whole-virus inactivated vaccine and each comparator under the conditions of this single-farm field trial.