What Is Herd Immunity

The existence of COVID-19 has introduced us to many new terms that we may not completely understand. One of those terms is “herd immunity.”

Herd immunity describes how the spread of a contagious disease can be controlled after a large enough portion of the population, (referred to as “the herd”) becomes immune.

A disease is most contagious when everyone in the community is at risk of contracting it. If a sizable percentage becomes immune however, it makes it harder for the disease to reach those susceptible because the herd blocks its ability to reach them.  As a result, the entire community becomes better protected.

There are two ways to achieve herd immunity: vaccination or infection and recovery.

  • Vaccination – Vaccines create immunity without causing illness or resulting complications. Vaccines have successfully controlled deadly contagious diseases such as smallpox, polio, diphtheria, rubella and many others. Herd immunity by vaccination protects people who are unable to be vaccinated due to age or other conditions.
  • Natural infection – Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection. For example, those who survived the 1918 flu (influenza) pandemic were later immune to infection to the H1N1 flu, a subtype of influenza A.

The percentage of a community that needs to be immune in order to achieve herd immunity varies from disease to disease. The more contagious a disease is, there will need to be a greater proportion of the population that is immune to the disease to stop its spread. For example, the measles is a highly contagious illness, therefore it’s estimated that 94% of the population must be immune to interrupt the chain of transmission.

It is important to note that while herd immunity can reduce the risk of getting a disease, it does not prevent it. Until an effective COVID-19 vaccine is developed, it is important to follow all safety guidelines to protect against the transmission of the virus, including:

  • Avoiding large events and mass gatherings.
  • Avoiding close contact with others, (within 6 feet).
  • Washing your hands often with soap and water for at least 20 seconds, or use an alcohol-based hand sanitizer that contains at least 60% alcohol.
  • Wearing a face mask or covering in public spaces.
  • Covering your mouth and nose with your elbow or a tissue when you cough or sneeze.
  • Avoiding touching your eyes, nose and mouth.
  • Avoiding sharing dishes, glasses, bedding and other household items if you’re sick.
  • Cleaning and disinfect high-touch surfaces daily.
  • Staying home from work, school and public areas if you’re sick, unless you’re going to get medical care.

All content of this newsletter is intended for general information purposes only and is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. Please consult a medical professional before adopting any of the suggestions on this page. You must never disregard professional medical advice or delay seeking medical treatment based upon any content of this newsletter. PROMPTLY CONSULT YOUR PHYSICIAN OR CALL 911 IF YOU BELIEVE YOU HAVE A MEDICAL EMERGENCY.