COLUMNISTS

Vaccines are useful tools, not the end all

Russ Daly
Mid Hudson Regional Hospital trauma program manager TJ Oltz prepares to administer the COVID-19 vaccine at the hospital in City of Poughkeepsie on December 15, 2020.

“When we have a vaccine ...”

You’ve heard this a lot over the course of the COVID-19 pandemic. Fill in the blank.

“When we have a vaccine, I can go to a ballgame again.”

“When we have a vaccine, we won’t have to worry about our loved ones getting sick.”

“When we have a vaccine, I won’t have to wear this mask.”

These promises are starting to become reality, with SARS-CoV2 vaccines being approved and distributed. Pretty soon, a significant number of people in our community will be able to say they’re vaccinated. This is by far the most encouraging development in a very discouraging pandemic.

As a veterinarian, especially one that helps people understand the role of vaccines in animal health, I’ve been following the COVID-19 vaccine news with interest. These vaccines employ some incredible new technology, and data shows they work very well, with 90-95% effectiveness. So far, I’m very bullish on these vaccines and their ability to safely stimulate the immune system in a vaccinated person.

But as a veterinarian who has administered thousands of vaccine doses to thousands of animals, I also know that vaccines aren’t without their potential limitations.

Veterinarians — who use many different types of vaccines against many different diseases in many different animals — understand that in some cases, vaccines are iron-clad necessities for disease control (e.g., rabies in pets). In other cases, they are useful tools (e.g., respiratory disease in cattle), and in others essentially worthless (e.g., Mycoplasma bovis in cattle).

There are several reasons for this variation in vaccine effectiveness across diseases, some depending on the germ and some on the vaccinated animal. Rabies virus is very different from other germs encountered by animals, so a vaccine can easily get the body to recognize it as foreign and attack it. As a result, rabies vaccines are incredible and essentially 100% effective.

For other animal diseases (bacterial pneumonia in cattle, for example), germs adapt to the body and can more easily hide from the immune system, even when animals are vaccinated against them. Cattle pneumonia is also a good example of a “complex,” which involves many different germs and external factors like weather and stress, making it a challenge for any one vaccine to work well. Even when a single novel virus is involved in a cattle disease, heavy germ exposures can overwhelm a perfectly administered vaccine program (Bovine Viral Diarrhea Virus in cattle reproduction, for example).

Veterinarians inherently know that for most conditions, it’s still possible for a vaccinated animal to get sick because of stresses that diminish the animal’s immune response or exposures that overwhelm the vaccine’s ability to respond. We also know that even if a vaccine works well enough to prevent severe signs of disease in an animal, that critter can still become infected and transmit the germ to others. In livestock groups, even if vaccines don’t work in 100% of the animals, we depend on them working well enough in enough animals to diminish the overall level of disease in the population.

I see similarities between our population-based approach to animal vaccines and the COVID-19 vaccines. I also sense a lot of misunderstanding among people regarding what we should and shouldn’t expect from the coronavirus vaccine.

We already know not to expect the COVID-19 vaccine to be 100% effective in everyone. If you’re vaccinated, there’s still a chance you’ll get sick, albeit a much smaller chance than if you weren’t vaccinated. Even if a vaccinated person doesn’t get sick, they can likely still become infected and spread the virus to other people.

What this means is that the COVID-19 vaccine is not a light switch that will magically turn off the pandemic. It’s a useful tool that everyone should take advantage of, and that will help reduce the spread. And you very well know the other tools: masks, social distancing and avoiding gatherings.

No cattle producer would vaccinate their calves against pneumonia and completely stop other disease prevention measures. They still treat and separate sick calves, protect against stresses, and prevent diseased animals from coming into the herd. They understand vaccines are a tool, not the end all.

Likewise, your COVID-19 vaccination doesn’t mean you can stop using the other tools. When COVID-19 transmission declines to the point where infections are uncommon, we can stop using those tools. The vaccines are going to help make that happen — but not if we ignore what else we need to do.

Russ Daly

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University.