Can the Microbiome Impact Immunizations

August is National Immunization Month, and rightfully so as we head into the fall season which is often accompanied by the flu and common colds. Immunization is often used interchangeably with the word vaccination. While our immune system works hard every day, sometimes it benefits from vaccines which provide a little extra assistance in establishing protection against diseases. The immune system is a complex network of various cells and organisms that work together to maintain good health and fight off infection. 

The immune system is broken into two branches: the innate immune system and the acquired immune system. The innate immune system provides the first line of defense to pathogens and is non-specific in its actions. The acquired immune system is activated when the innate immune system is unsuccessful as it targets the specific pathogen, creates antibodies, and is more effective. Immunity can be achieved by either natural immunity which involves direct infection with a pathogen or vaccine-induced immunity, which involves the introduction of a weak or killed pathogen into the body. Both natural and vaccine-induced immunity results from stimulation of the immune system to create specific antibodies which help the immune system “remember” that pathogen should it be encountered in the future (1).

How do Vaccines work?

Vaccinations are extremely important to the health of both humans and animals. There are several core and recommended vaccines for our pets that help prevent both illness and death and include those that help protect against diseases that are considered zoonotic. Zoonotic diseases are diseases, such as rabies and leptospirosis, and can be transmitted from animals to people.  By maintaining our pet's vaccinations, we also help protect ourselves as well.  

For a vaccine to be effective, not only does it have to be administered, but the patient must also have an appropriate immune response to create the intended protective immunity. So how exactly do vaccines and the immune system work together to create effective immunity? That is a complex question that cannot be answered in a simple blog. Various factors such as age, underlying health conditions, environmental factors, and genetics can all influence the effectiveness of a vaccine (2). As you may already know, many of these factors, along with antibiotic use and diet, also influence the health of the gastrointestinal microbiome which is comprised of various microorganisms, also known as microbiota, and other cellular components which are actively involved in regulating immune responses. These immune responses manage a delicate balance of initiating action against harmful pathogens while tolerating harmless pathogens (3). 

Does the microbiome potentially play a role in vaccine efficacy?

When studying the microbiome and its impact on the immune system, germ-free mice are often used as these mice lack all microorganisms including those which normally inhabit the gut. As may be expected, research has shown that there are deficiencies of certain immune cells and functions within the gut in germ-free mice. Antibody production is also decreased but can be improved once normal microbiota are established in these mice (3). 

Another study revealed that immunized germ-free mice and antibiotic-treated conventional mice had decreased immune responses to a vaccine compared to normal mice. Once microbiota colonization occurred, the germ-free mice mounted an enhanced immune response post-vaccination (2). Similarly, a study that examined the immunity of mice administered antibiotics post rabies vaccination; found that these mice had reduced numbers of rabies-specific antibodies compared to the group not treated with antibiotics (4). This indicated the level of immunity post vaccine was not as high in the group which received antibiotics. 

Summary

There is no doubt that maintaining vaccines in our pets helps improve their longevity as well as protects the general pet and human population. The microbiome has proved to be a powerful regulator of overall health. Keeping a healthy microbiome will help support overall health and wellness in both us and our pets. Perhaps it will even help support and maintain protective immunity to vaccines. While there is still a lot that is unknown regarding how the gut microbiome regulates the immune system and contributes to vaccine efficacy, it is exciting to think of where future research will lead us.