With the plethora of beef recalls over recent years, companies and scientists are teaming up to develop pre-harvest vaccines for livestock used for food.  Pre-harvest vaccines are administered to livestock to minimize the presence of naturally occurring bacteria within the ruminants that can cause human illness.

“There are animal health products under development to target organisms that may cause foodborne illness in people.  Some of these products may come to market as drugs regulated by FDA and others may be biologics regulated by the USDA,” said Kent D. McClure, General Counsel for the Animal Health Institute.

Pre-harvest vaccines have been discussed for years amongst animal health officials. Research and development has focused for some time in the area of animal agriculture in order to increase safe animal processing, McClure explained.

Previous vaccines have failed because of the time and costs associated with research and development as well as the difficulty in creating vaccines that deal with a broad range of illnesses, explained Professor Peter Davies from the University of Minnesota’s Department of Veterinary Population Medicine.  

“For a conventional animal health product, i.e. one that is developed to address an illness within livestock, it can take a pharmaceutical company six to eight years to bring the product to the marketplace,” said McClure.  “It takes a $40 to $100 million investment and typically another six to eight years to recoup the investment,” he said.

Davies agreed with McClure in that pre-harvest vaccines are a good idea, but explained further that vaccines are very difficult to create because of bacteria stereotypes. 

“Until now, there has been virtually nothing out there that will work.  There are so many stereotypes of bacteria, and vaccines are specific to individual stereotypes.  In the past, vaccines haven’t protected on the broad scale because of the diversity of foodborne pathogens,”  Davies told Food Safety News.

Examples of pre-harvest drugs currently on the market include an E.coli O157 vaccine for use in cattle and Salmonella enteritidis vaccine for use in chickens.

In addition to development issues associated with pre-harvest vaccines, regulatory hurdles exist.  Products that are developed for livestock, but aim to prevent illness in humans are a completely new category of drug, and therefore it is unclear if once developed, vaccines will have to undergo regulatory review by the Food and Drug Administration (FDA) or the U.S. Department of Agriculture (USDA).  

“Regulatory systems that license animal health products have developed to ensure the safety and efficacy of the products.  They [vaccines] are usually evaluated as stand-alone interventions and have not typically been considered as part of a chain of interventions,” McClure said.

“However, pre-harvest animal health products are intended to be a tool in the chain of interventions, including the hugely successful HAACP program, to act in concert to further decrease potential human exposure to food borne pathogens,” McClure explained.

The creation of vaccines deemed successful by the USDA could mean that the vaccines are given conditional licensure to address unmet needs.  In order to be granted this status, a manufacturer must show the USDA that the product is safe and that it has a reasonable expectation of efficacy.  The product is then marketed while field studies are conducted.

McClure also stressed that the vaccines will not harm animals in any way.  “They are intended to decrease the level of organisms that are often normal inhabitants of the animal’s gastrointestinal tract, but are important from a human food safety perspective,” he said. 

Professor Davies explained that though the vaccines do not harm the animals, the immune system is designed to keep naturally occurring bacteria in check, not eradicate it. “We’re asking the immune system to do things they’re not designed to do.  We’re asking bacteria to stop invading the body.”

As for the future of pre-harvest vaccines, “We are confident that over time these pre-harvest products can be developed for a range of pathogens and species.  These promise to be important on-farm tools to help in the battle against foodborne illness,”  said McClure.