Back to basics: fundamentals drive vaccine performance

17 December 2025

6 minute read

By: Sarah Mikesell

At a time when disease pressure continues to challenge pork production systems across the United States, vaccination remains one of the most valuable and heavily discussed tools available to veterinarians and producers.

Speaking at the 2025 Four Star Pork Industry Conference in Muncie, Indiana, Dr. Daniel Gascho, veterinary partner of Four Star Veterinary Service and owner of Swine Health Care in Mexico, Indiana, encouraged the industry to return to fundamentals in how vaccines are selected, handled and administered across sow farms, gilt development units and grow-finish operations.

Gascho acknowledged at the outset that vaccination can quickly become a technical and sometimes tedious topic. But real-world execution, not complex immunology, is where most vaccine failures occur.

Gascho said his goal was not to dictate specific protocols, rather he hoped to remind producers and farm managers that it’s the things that we do every day – so often that they become repetitive – and we don't stop and think about why we're doing it or how we're doing it or how we should do it. Instead of prescribing a one-size-fits-all formula, Gascho urged attendees to evaluate how vaccine strategies are actually carried out on-farm, and to openly engage veterinarians and industry partners in discussion to get their perspective of how you and your team are doing.

“Every scenario is different, and your best action is to start a conversation with your veterinarian to form a protocol that fits your farm,” he said.

“Don’t kill the vaccine” – a critical theme

Gascho repeated one message throughout his presentation, noting it is the #1 cause of failed vaccine performance.

“With live vaccines, don't kill the vaccine,” he stressed. “I'm not going to dive into the details, but especially with oral live vaccines. Keep in mind that if you have a medication either in the feed or water that is intended to be active against that type of pathogen, don't run something at the same time that will kill the vaccine.”

He warned that everything from the temperature of the water used to thaw the vaccine to medicated feed residues can ruin a product before it ever reaches the pig.

“If you kill your vaccine, you might as well inject them with water, but it might actually be worse than that,” Gascho said. “With some of these vaccines, if you mishandle them such as freezing them or letting them get too warm, they might actually cause reactions to the pigs that would be worse than just dumping them in the pit.”

Gascho recommended flushing medicator lines, verifying water medication withdrawal windows and accounting for vaccine bottle concentration and the amount of time it takes for every pig to have access to their dose.

Live vs. killed vaccines: two categories, very different expectations

Gascho emphasized that one of the most common sources of confusion – and failure – begins with a misunderstanding of the fundamental differences between live vaccines
and what are traditionally called killed vaccines. However, the category of “not live” vaccines includes more than just killed products.

“If we want to be technical, we also have vaccine technologies that are on DNA plasmids or mRNA vaccines that technically were never even alive, so they are not killed,” he said.

Understanding how these products behave inside the pig and what they need in order to work is essential for producers making decisions about labor planning, booster timing and product selection.

Live vaccines

Many swine operations depend on live vaccines for challenges such as PRRS, ileitis and oral E. coli. Their effectiveness depends entirely on two factors: timing and survival of the live organisms.

“If you want your vaccine to work, you need to give it far enough ahead of the challenge, when possible, to allow time for the vaccine to replicate or colonize the cells in the body,” he said.

He recommended three or more weeks before expected exposure for most live products, acknowledging that perfect timing is sometimes not realistic. 

“I know we don't all live in a perfect world and usually somebody will fire back at me that if I'm going to vaccinate these pigs prior to the exposure by three weeks, then I'm going to vaccinate them in the uterus,” he said.

One significant exception is oral E. coli vaccines, which operate primarily through competitive inhibition in the gut. Unlike traditional live vaccines, they must be administered close to the expected challenge.

“These vaccines aren't pathogenic, but if you administer too far ahead, it did its job but then has cleared out and is no longer protecting when the true challenge comes along,” he explained.

Killed and “not live” vaccines

Killed vaccines behave very differently and require producers to plan ahead and expect gradual immune response development.

“The simplest rule of thumb is these vaccines don't competitively inhibit anything; the pig’s body has to take up the actual product and that's going to take some time,” he explained. He repeated the importance of working ahead of the challenge curve.

“It's pretty safe to say that anything injected into an animal often takes close to three weeks to be fully recognized and generate immunity,” he said.

Boosters can significantly increase duration or peak immunity and are required for some products such as pre-farrow gilt scour vaccines to work at all, he added.

“A single dose is unlikely to generate enough immunity to where they will get protective immunity from their mom while nursing,” he noted.

Even though killed vaccines cannot be rendered inactive by antibiotics in the same way that live vaccines can, Gascho warned that storage temperature and sunlight exposure still matter.

“We can definitely deactivate or ruin our vaccines, even the killed vaccines,” he said.

Disease-specific timing considerations in sows, gilts and growing pigs

Gascho provides a brief overview of common vaccine categories and practical timing considerations.

Circovirus – Given at weaning or sometime prior to PCVAD. Barring an overwhelming viral load, usually a full injected dose at weaning will hold a pig until market. Booster split-dose strategies can extend or increase coverage if needed.

Mycoplasma hyopneumoniae – Can be separate in certain scenarios, but often given in combination with circovirus vaccines, when needed. Some flows may be myco-negative.

Ileitis – Producers may use injectable or oral vaccination depending on flow status and labor capacity; the tradeoff is convenience versus confidence in dose delivery.

PRRS – Strategies vary widely based on risk level, stability and production goals. May need to periodically booster in breeding herds as immunity wanes. Single dose may hold to market in finishing pigs.

Reproductive vaccines – Help reduce stillborns, mummies and conception failures. Strategies range from annual boosters to every-parity timing. High health herds may need less, but generally, gilts need some booster at arrival.

Pre-farrow scour vaccines – Gilts require particular attention because they are immunologically naïve. Don't forget to booster animals that are completely naïve if you want the pre-farrow shot to generate the response that you're looking for. Final dose should be (depending on product) 2-3 weeks pre-farrow to create peak immunity at the time of colostrum production.

Influenza A – Flu is highly strain-specific and difficult to manage across different phases of production. May want to consider creating a vaccine that is specific to your farm or area. Pre-farrow can generate colostrum immunity but can interfere with vaccination of the babies.

Autogenous and bacterial vaccines – Due to strain variation, generic vaccines do not usually match on-farm pathogens. Vaccines need to be a specific match to your operation.

Takeaways

Gascho closed with key takeaways, reminding attendees not to chase universal solutions. 

“There is not a single vaccine protocol or a correct way to do it,” he said. “Match it to your farm, your scenario, your risk and your goals.” He reinforced that successful vaccination relies on execution more than product selection.

“If you're going to spend your money on a vaccine, handle it right, give it at the right time, so that it wasn't just a complete waste of your time and money,” he said. And one final message — repeated again to emphasize its importance: “don't kill the vaccine.”

Through careful planning, disciplined execution and collaboration with veterinarians and suppliers, he said, producers can improve consistency, protect herd health and ensure every vaccination dollar achieves its intended purpose.