Licensing requirements assure pure, safe, potent and effective vaccines

CENTENNIAL, Colo. — Creating a pathway to license new, safe and effective animal vaccines is the focus at the U.S. Department of Agriculture’s Center for Veterinary Biologics.

“My job is to evaluate new vaccines proposed for licensure,” said Bruce Thomsen, senior staff veterinarian for the CVB.

“There are new disease challenges and old diseases that we don’t have good vaccines for, so this creates a strong need for new and better vaccines,” said Thomsen during a webinar hosted by the National Cattlemen’s Beef Association.

The mission at the CVB is to determine if the vaccines are pure, safe, potent and effective.

“That means we know and understand everything in the bottle of vaccine, we have tested it on animals and other tests to prove it’s safe in the environment, the vaccine has the right amount of active ingredients and the manufacturer has done the studies to prove the label claim,” Thomsen said.

Safety evaluations start the first time the CVB officials talk to the vaccine manufacturer.

“For the pre-license safety requirements, we ask for a wide variety of safety studies and our laboratory does testing on the vaccines,” Thomsen said. “We also inspect the manufacturing facilities to make sure they’re following the processes.”

For the post-license safety requirements, the CVB monitors the manufacturing facility, monitors the sales and collects the adverse events.

“We determine vaccine safety based on risk assessment,” Thomsen said. “A hazard is something that has the potential to cause harm, while the risk is the likelihood of harm occurring.”

During the risk assessment, the CVB looks at three key areas — intended animal species for the vaccine, public health safety and environmental safety.

“For the species, we predict adverse events by what we know about similar vaccines and we look at specific situations that might be a higher risk,” Thomsen said.

“For public health safety, we look at the probability of human exposure and we do the same thing for the environment to see if the vaccine could spread in the environment.”

If there are risks associated with a vaccine, warning statements are put on the labels or restrictions put on the products.

“An example is some animals might have an allergic reaction or there is a risk of an abortion if used in a pregnant animal,” Thomsen said.

The licensing process typically takes a couple of years, the veterinarian said.

“If we see issues that cause us concern, we may stop the licensing process,” he said.

Immune System

The point of a vaccination is to protect the cow’s immune system, said Amelia Woolums, doctor of veterinary medicine and professor at Mississippi State University.

“The immune system has to protect the cow against a wide variety of bacteria, viruses, parasites and fungi,” she said.

The goal is to keep these organisms out of the cow.

“But if they get into the cow, the immune system has to clear them without harming the cow or her unborn fetus,” said Woolums, who also spoke during the NCBA webinar. “It’s an amazing feat the immune system carries out without us thinking much about it.”

There are several types of vaccines, including killed, modified live and toxoids.

“There are also DNA vaccines for use in poultry and RNA vaccines that are licensed for use in swine,” Woolums said.

“Modified live vaccines have been fantastic to help prevent disease due to a lot of different infectious agents,” she said.

“But they can have problems because sometimes the modified live vaccine can be too much like the infection and the cow might develop a fever, go off feed or have other problems.”

Sometimes killed vaccines don’t induce effective immunity, Woolums said.

“RNA vaccines are an option between a modified live and a killed,” the university professor said.

“One of the real pros to RNA vaccines is they provide the benefits of modified live vaccines without the risk of modified live vaccine whole virus exposure,” she said. “They can be safer in terms of less reactive, but also more effective than killed vaccines.”

So, if a vaccine manufacturer knows the proteins that are important for immunity to a virus or bacteria, Woolums said, RNA vaccines can be made very quickly.

“A con of RNA vaccines is they may require carriers made of lipids and proteins to ensure effective immunity,” she said.

“These are similar to adjuvants that are in currently available vaccines and figuring out the right carrier can take time and money.”

Therefore, RNA vaccines are more expensive to manufacture than modified live or killed vaccines.

“But prices of a lot of things go down the more we make them, so we may find RNA vaccines are cost-effective in the near future,” Woolums said.

“Cattle producers need innovative approaches to provide effective vaccines that can be available in a short time frame,” she said.