Efficacy of a live intranasal vaccine against parainfluenza type 3 and bovine respiratory syncytial virus in young calves with maternally derived antibodies.

Trial Design: Two randomised controlled vaccination trials with artificial challenges were carried out in addition to a serological survey of levels of maternally derived antibodies (MDA) to parainfluenza type 3 virus (PI3V) and bovine respiratory syncytial virus (BRSV) in European calves.

Participants: Ten-day-old calves with and without MDA were included in the two vaccine trials.

Interventions: Intranasal administration of a bivalent modified live (PI3V/BRSV) vaccine followed by artificial challenge approximately three months post vaccination.