mRNA vaccines

What Are mRNA Vaccines in Veterinary Medicine?

I’ve recently been asked about mRNA vaccines in veterinary medicine, and whether they are fundamentally different from the vaccines we have used for years. The short answer is: not really!

At the most basic level, vaccines work by exposing the immune system to something that allows it to recognize a particular pathogen and produce an immune response. Ultimately, it is a protein (or protein-containing antigen) that is recognized by the immune system and stimulates antibody production.

The difference between vaccine types is largely how that protein gets into the body and is presented to the immune system.

With killed and subunit vaccines, the relevant proteins are already contained in the vaccine. These vaccine components are taken up—or phagocytized—by immune cells. Those cells process the proteins and present pieces of them to other immune system cells, initiating an immune response and antibody production.

With modified-live and viral-vector vaccines, the vaccine organism or vector enters cells and uses the cell’s machinery to produce the relevant proteins. Those proteins are then presented to the immune system.

mRNA vaccines work on a similar basic principle. Instead of putting the finished protein into the vaccine, the vaccine delivers messenger RNA (mRNA), which provides temporary instructions for our cells to make the specific protein. The immune system then recognizes that protein as foreign and mounts an immune response.

One potential advantage of this approach is that it can be designed to produce a more specific immune response directed toward a particular antigen. In theory, a more targeted response may reduce unnecessary immune stimulation and could make the vaccine safer. However, safety still depends on the specific vaccine, its ingredients, how it is delivered, and how an individual animal responds. “More specific” does not automatically mean risk-free, and every vaccine must be evaluated for both effectiveness and safety.

So while the technology used to deliver the antigen is different, the basic goal is the same: get the immune system to recognize a specific protein and develop immune memory against it.

This is not a completely new concept in immunology. Vaccines have always used different approaches to accomplish essentially the same thing—show the immune system what to recognize without causing the disease itself.

As with any veterinary vaccine, the important questions are how effective it is, how safe it is, what disease it is designed to prevent, and whether it is appropriate for the individual animal.