Efficacy evaluation of the C-strain-based vaccines against the subgenotype 2.1d classical swine fever virus emerging in China.

•The efficacy of C-strain vaccines was evaluated against the subgenotype 2.1d CSFV emerging in China.•C-strain vaccines adapted to continuous ST cell line (CST) contain a unique M290K variation on the E2 protein.•There were antigenic differences between CST and CBT or CRT.•C strain could provide clinical but not pathological and virological protection against the subgenotype 2.1d CSFV.