as skycat said but the main reason vet jab twice is becauce they jab to young and they tend to jab for parvo and then lepto in a seperate jab , some pups jabbed at 8 weeks wil just piss out any benifits of the jab its better to leave them to 10 --12 weeks then jab them , if an 8 in 1 jab is used then you only need to jab once , brian if you want bring it around here and i ll jab it or you