Vaccines utilize new technologies
Inactivated vaccines were the first form of injectable livestock disease control, but when new technology created modified live vaccines, many producers switched, as at the time they were considered more effective.
However, inactivated vaccines today have improved, and offer a much higher level of control than they did historically, says Dr. H. Nielson, DVM, of Novartis Animal Health. Prior to his association with Novartis, Nielson practiced in Utah for 31 years.
“Historically, there were a couple problems with inactivated vaccines. One being that during the inactivation process the protein of the virus they were trying to stimulate was destroyed. This resulted in a vaccine for a bug that didn’t look much like the bug infecting the host animal.
“Another problem was that they had a carrier that was allen-based and didn’t stimulate the immune process well, so we had a vaccine that didn’t look much like the disease we were trying to prevent, because it was destroyed during the inactivation process and it didn’t stimulate the immune system,” explains Nielson.
When modified live vaccines became available, they were grown in the body and stimulated the body more effectively for the disease. But, as with inactivated vaccines, they weren’t without problems.
“Sometimes modified live vaccines would get wild strains that resulted in a disease even worse than the one we were trying to prevent. There are times that’s still a problem,” comments Nielson.
Other problems associated with modified live vaccines include abortions in cattle when the cow isn’t vaccinated properly.
“New inactivated vaccines are an adjuvanted product and use an oil-based carrier and can stimulate an immune response better. It’s also an intact organism that invades the body, which creates a better response to the disease,” says Nielson.
He explains that a lot of improvements to livestock vaccines were made when HIV came front-and-center in the world of human medicine.
“They wanted to produce a vaccine that would be advantageous and prevent infection, so they started developing adjutants, or carriers, with the idea to inactivate the virus and still stimulate the immune system. There were no takers on doing that with HIV, but the development of those carriers became first and foremost in the effort to drive the immune system with a vaccine that was inactivated and completely safe,” explains Nielson.
According to Nielson, there is a place for both inactive and modified live vaccines in the livestock industry today.
“As an industry we’ve gotten too far to one side, where everyone thinks it has to be modified live or it doesn’t work. That just isn’t the case with these newer inactivated vaccines,” he says.
Nielson suggests, as a rule of thumb, using modified live vaccines when developing young animals, especially breeding heifers. Then, once that female enters the cowherd, inactivated vaccines can be used for the rest of her life.
“It’s important to realize that both sides of vaccinology are important and stimulate the immune system. It’s a matter of using the vaccines at the proper time in the proper type of animal,” he adds.
As for what’s next in the vaccine world, Nielson says technology is definitely evolving.
“Next will be site specific vaccines, where they will stimulate an immune response specifically where the virus invades the body. Vaccines will also continue to be driven orally at some time and maybe inter-nasally. Long term will be feeding of antigens and having them target the sites where the virus would be most active,” he says.