“When we’re talking vaccines, the worst-case scenario is not vaccinating,” says Idaho County Extension Educator Meranda Small. “That means you’re not giving your animals the opportunity to be set up for success in a variety of scenarios.”
But just going through the motions is not what will set your animals up to impress at the saleyard or feedlot. Producers need to make sure they are giving vaccines in a way that lets the animals get the good out of them.
Two distinct types
The distinction between modified-live vaccines (MLV) and killed vaccines is important to keep in mind. They work differently, and the animal responds differently.
In a killed vaccine, the manufacturer uses high temperature, ultraviolet light or another mechanism to kill the disease-causing organism – usually bacteria – while making the product, says Lauren Christensen, DVM and assistant professor of mixed practice production medicine at the University of Idaho (U of I). However, she says, “The shape of the bacteria is still there. That allows the body to recognize it and mount an immune response.”
Because dead bacteria are incapable of replicating or causing harm to the animal, killed vaccines must also include an adjuvant, often aluminum-based, that causes local irritation. This may cause physical signs, like injection-site swelling. Irritation triggers the immune system to get to work fighting the “pathogen” found in the vaccine so it can recognize the shape later.
MLV, which require mixing, contain bacteria or viruses that are still live but have undergone attenuation. This process yields a pathogen that “is unable to set up a full-blown infection but can replicate to some degree,” says Catherine Dowling, Zoetis beef technical services veterinarian for the Pacific Northwest.
The MLV stimulates the immune system better than a killed vaccine, even after one dose. “The animal mounts a comprehensive, robust immune response,” Dowling says.
Because of that response, producers may see side effects such as quietness or reduced appetite, says Christensen. This is also why MLV are typically recommended for open cattle. “We can see transient infertility or abortion in cattle that have never had MLV products before,” says Christensen. “It causes the whole animal to have an immune response that can interrupt blood flow to the reproductive system.” Ideally, MLVs are usually not given within three weeks of breeding.
This inflammatory response is not a negative side effect. It’s exactly what they are designed to do and what makes them more effective in fighting disease when given according to label instructions. “MLVs are still very safe,” says Dowling. “They just have more stringent guardrails in place.”
Keeping an eye on the cooler
One guardrail in place for both types of vaccines is recommended storage temperature. “Temperature excursions are harmful to all products,” says Dowling. These include exposure to temperatures either above or below the range listed on the bottle. Impact may vary with product, the extremity of the excursion and how long the vaccine was exposed.
A particular caution to keep in mind is that freezing disrupts the vaccine on a chemical level. “Obviously, there is a continuum between seeing some ice crystals floating around in the bottle versus a solid block of vaccine,” says Dowling. If producers know a product has been exposed to temperatures outside the “safe” range, she recommends calling the manufacturer’s support line for recommendations unique to that vaccination line.
Generally speaking, if ice has formed to enough of an extent to disrupt the composition, says Dowling, “The best-case scenario would be rendering the vaccine ineffective. In that case, the protection offered is less than ideal, or nothing.”
In the worst-case scenario, ice crystals rupture components of the vaccine. “When we freeze and thaw stuff, we can see damage at the cellular level,” says Christensen. “Think about what happens to frozen lettuce or tomatoes.”
When a killed vaccine contains gram-negative bacteria, such as those for scours, vibrio-lepto and some respiratory diseases, ruptured cells can release endotoxins into the vaccine solution. “These [endotoxins] are part of the bacteria,” says Dowling. “When you have a complete cell, it’s no problem. When released, it’s a problem.” These free endotoxins can cause symptoms Dowling describes as “clinically indistinguishable from anaphylaxis.”
What about anaphylaxis?
While most producers probably have a bottle of epinephrine or steroid tucked away in the refrigerator or vaccine cabinet – just in case – the odds of seeing a true anaphylactic reaction are pretty low. “The animal has to have seen that product or a version of that product before,” says Dowling. Anaphylactic shock is an immune response to any product – vaccine, implant or otherwise – and not indicative of an issue with the product itself. “We can see these responses even in healthy animals and with products that have been handled appropriately,” she says.
“I’ve seen it a couple times in my professional career,” says Small. Only one of those was fatal. Like reactions to frozen vaccine, the risk is small enough that it shouldn’t deter producers from vaccinating their animals. But, says Small, “It is worth being aware of what anaphylactic response looks like and what to do if it happens. Read the label and talk to your vet.”
Final considerations
If an issue does occur with a vaccine (or other product), both Christensen and Dowling recommend reaching out to the manufacturer. “Are negative reactions common? No. Do we like to be informed about it when they do happen? Yes,” says Dowling.
Feedback helps Zoetis identify whether there are issues in the way vaccine is handled along the supply chain. “It’s a reminder to producers to record lots and serial numbers,” she adds. If necessary, these numbers allow them to detect issues affecting multiple producers.
But often, when problems do occur, they are exacerbated by animal stress. It is common to vaccinate at branding, weaning or other already high-stress situations – avoiding additional stresses, such as extreme weather, can set animals up for success. “Make sure animals are hydrated and in the best shape they can be in to mount an immune response,” advises Christensen. “The immune system takes a huge amount of water.”
Small also recommends producers stay abreast of updates in disease and pest management. “We get really set on, ‘This is our protocol,’ and we don’t evaluate it,” she says. “We need to be keeping in constant conversation with our vet to make sure we’re not getting complacent.”
