Viral challenge determines if vaccines work
Vaccines are very efficient and critical components to the health of the world, as long as you use them correctly and know their limitations. The majority of people think that once you have a vaccine, or administer one to an animal, then they/it are protected. This is true to a point and it depends on the virus. Here is a good example:
There was a study that showed when an animal was only exposed to a BVD-PI animal for a day, the vaccine was 100% effective. Yet, when exposed to a BVD-PI for a week the vaccine was only 70% effective.
Vaccines work by making the body produce antibodies against it. Vaccines look very similar to the true virus, so when the animal gets exposed to the real thing down the road, the body will know how to fight it. There is one big problem with BVDV and BVD-PI animals: they produce so many virus particles that it overwhelms the immune system and “over powers” a vaccine.
There is a second problem with vaccines, the body needs a 10-14 days to build a response to the vaccine, it takes around 30 days (and possibly a booster) to get the full benefit. So, lets say you get a load of calves in. You give them a BVDV vaccine during processing but they are still having problems. This is because they have not had enough time to build antibodies to the vaccine by the time they were exposed to overwhelming amounts of the virus.
There is one thing that is 99.99% effective against BVDV, that is testing for and removing BVD-PI animals. If you remove the problem all together, vaccines work like they are supposed to.
Follow us as we explore what COVID and BVD have in common and how we can take what we have learned from COVID and apply it to our beef operations.