Fetal protection is defined as “the ability to prevent transplacental transmission of BVDV and subsequent fetal infection in pregnant cattle”.

Fetal protection is determined generally by experimental infection of vaccinated pregnant animals at 75 days of gestation. The USDA has published requirements for vaccine manufacturers to following in determining the fetal protection and labeling guidelines of BVDV vaccines, Center for Veterinary Biologics Notice 02-19. may vary depending on the infecting BVDV. A vaccine may provide different levels of protection to the fetus when different BVDV viruses are used for virus challenge.

For example, persistently infected calves may occur in only 10 to 15 % of vaccinated animals when 1 certain virus is used to experimentally infected pregnant animals and when only BVDV is used to experimentally infected pregnant animals, 35 to 50 % of the vaccinated animals may give birth to persistently infected animals.

Complete (100%) vaccination against all BVDV is not possible. Therefore, in addition to vaccination, preventing exposure to BVDV during pregnancy is also warranted.

Vaccination of breeding animals should also be directed at providing protection of the fetus.

The ability of vaccination to prevent fetal infection is important in reducing the potential for transmission.