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Published on April 25, 2019

What Is Herd Immunity and How Does It Protect Us From Disease?

Herd Immunity

Recently, the term “herd immunity,” or “community immunity,” has become more common in conversations about vaccinations. Just as a herd of sheep or cattle protects itself from danger by using sheer numbers, we can protect ourselves and our communities from sickness by getting as many people vaccinated as we can.

Herd immunity happens when a big enough part of a population gets vaccinated against a virus or bacteria. This makes it difficult for the virus or bacteria to spread because there are so few unvaccinated people left to infect. Herd immunity can effectively stop the spread of a disease.

Through herd immunity, vaccinations also protect people who are unable to be vaccinated due to age or immune status or concurrent illness. These include newborns, the elderly, people without a fully working immune system, people receiving chemotherapy treatments, people with HIV and those who are very ill in the hospital.

Society today is full of crowded places where germs can be easily spread from one person to the next. People are also traveling more often to areas around the world where certain illnesses, such as measles or chickenpox or more common or where there is limited access to vaccines in comparison to the United States. Because of this, each one of us who is healthy enough to be vaccinated must do so. If too many people go unvaccinated, there are opportunities for viruses and bacteria spread and make people sick. A current example of this includes measles outbreaks we are seeing in New York, Washington and Oregon. We are seeing the highest number of measles cases in the U.S. in twenty years due to decrease in vaccinations in certain communities.

It has been proven time and again that people get sick less often in areas with high vaccination rates. Vaccinations protect more than just the person who receives the vaccination. It helps protect whole communities from becoming sick, and in some cases, can even eradicate a disease. That is why having yourself and your family vaccinated is so important. You are doing your part to keep our communities healthy and out of danger. If you are traveling to a region that is known to have communicable disease such as measles, check with your physician to ensure you are vaccinated.

Here is a list of common vaccines used in the United States:

Hepatitis A
Hepatitis B
Haemophilus influenzae type b (Hib)
Human Papillomavirus (HPV)
Seasonal Influenza (Flu)
Typhoid Fever
Varicella (Chickenpox)
Yellow Fever

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About the Author

What is Herd ImmunityCynthia B. Snider, MD, MPH practices Infectious Disease and Internal Medicine at the Cone Health Regional Center for Infectious Disease