Longitudinal field study of the effect of a commercial porcine circovirus type 2 vaccine on postweaning mortality in New Zealand farms

Materials and methods: In 2007, a PCV2 vaccine recommended for use in piglets ≥ 4 weeks of age was made available in New Zealand for control of porcine circovirus associated disease (PCVAD). The effectiveness of vaccination in reducing mortality attributed to the disease was determined on nine farms that met the New Zealand case definition for postweaning multisystemic wasting syndrome (PMWS), a specific clinical expression of PCVAD. During 2006 and 2007, mortality data were collected from 138 groups of pigs affected by PMWS but not vaccinated and 67 groups affected by PMWS but immunized with PCV2 vaccine. Historical data were available from 130 groups on the study farms prior to the appearance of PMWS.