When forest fire experts want to proactively decrease the risk of wildfires, they create small, controlled burns to limit the amount of fuel available to the fire. This reduces the fire’s ability to spread. The concept of controlling infectious disease is similar. Experts credit vaccinations for playing a large role in the decline of communicable diseases, notably for the complete eradication of smallpox. When people receive recommended vaccines, they generally become immune and, and viruses and bacteria cannot spread from individuals into the community. Fire checked! This is the premise of herd immunity.
Amira Roess is an emerging disease epidemiologist and professor of global health in George Mason University’s College of Public Health. Roess explains what herd immunity is, how it works, and its importance in maintaining control of infectious diseases.
What is herd immunity?
Herd immunity is what occurs when the majority of a population, over 95% for most diseases, becomes protected against a disease. When this happens, the virus or bacteria essentially hits a dead end of people to infect and spread stops.
How is herd immunity achieved?
Immunity occurs after a harmful virus or bacteria, what we’ll call a “bad bug,” that can make you sick enters the body either through infection or vaccination. After that exposure, our immune system will produce antibodies to fight against that bad bug. When you are exposed to that bad bug again your body remembers and more quickly activates to produce antibodies to fight back. This is essentially how your immune system works.
As more of us become immune, the bad bug runs out of people to infect and sizzles out. For every person who is immunized, it becomes that much more difficult for the disease to cause additional sickness.
Vaccines have been developed to kick-start that active immunity in a safer proactive way rather than risk severe illness from infection. For example, measles used to kill hundreds of children a year and now because of vaccination we almost never see measles deaths among healthy, vaccinated individuals.
What is the role of vaccinations in herd immunity?
Over the last several decades, we have used vaccines to proactively protect people from infectious diseases. Vaccines work by introducing a weakened or inactive version of the disease-causing agent to the body to trigger active immunity.
Vaccines have been proven to be safe and effective. Research shows that any side effects from vaccines are minimal and far less harmful, and short-lived, compared to actually having the disease.
If others are vaccinated, why should I have to?
If you are able to be vaccinated, you absolutely should. Disease causing viruses and bacteria require a non-immune host to spread and survive. If infections are allowed to circulate unchecked, we run the risk of mutations that render vaccines ineffective.
Herd immunity through vaccination prevents unnecessary disease spread and deaths. If we rely on attempts to reach herd immunity through exposing people to a virus, it results in unnecessary deaths. There are a lot of people who are immunocompromised, and their bodies can’t fight back if they get infected. They can’t produce antibodies that are strong enough to fight the bad bugs. These individuals rely on the rest of us getting vaccinated. Opposition to vaccination is contributing to outbreaks, which are sickening and killing mainly unvaccinated individuals.
Many infectious diseases are largely preventable. Why risk it when vaccine interventions are available?
Why are many recommended vaccinations for diseases that I’ve never known anyone to have?
Herd immunity and vaccines! Diseases like measles, mumps, and rubella used to kill many people, especially in children, before their vaccines were created and herd immunity was achieved.
##
MEDIA INQUIRIES: For reporters who wish to speak to Amira Roess about herd immunity or infectious disease spread, please email media contact Michelle Thompson at mthomp7@gmu.edu.
Amira Roess is a professor of global health and epidemiology at George Mason University's College of Public Health, Department of Global and Community Health. She is an epidemiologist with expertise in infectious diseases epidemiology, multidisciplinary and multi-species field research and evaluating interventions to reduce the transmission and impact of infectious diseases. Roess currently oversees several longitudinal studies to understand emergence and transmission of zoonotic infectious diseases globally, including the emergence and transmission of Campylobacter (with support from The Bill and Melinda Gates Foundation), MERS-CoV (with support from the U.S. National Science Foundation), and the development of the microbiome during the first year of life. She studies links between food animal production and emerging infectious and zoonotic diseases emergence globally, and mHealth (especially apps) technology integration and evaluations to reduce the impact of infectious disease outbreaks, promote health care, and help reduce disparities.
About George Mason University
George Mason University is Virginia’s largest public research university. Located near Washington, D.C., Mason enrolls more than 40,000 students from 130 countries and all 50 states. Mason has grown rapidly over the past half-century and is recognized for its innovation and entrepreneurship, remarkable diversity, and commitment to accessibility. In 2023, the university launched Mason Now: Power the Possible, a one-billion-dollar comprehensive campaign to support student success, research, innovation, community, and stewardship. Learn more at gmu.edu.
About College of Public Health at George Mason University
The College of Public Health at George Mason University is the first College of Public Health in Virginia and a national leader in inclusive, interprofessional, public health research, education, and practice. The college is comprised of public health disciplines, health administration and policy, informatics, nursing, nutrition, and social work. The college offers a distinct array of degrees to support research and training of professionals dedicated to ensuring health and well-being for all. The college’s transdisciplinary research seeks to understand the many factors that influence the public’s health and well-being throughout the lifespan.
Thumbnail by Centers for Disease Control and Prevention Public Health Image Library via Unsplash.