This is How Hedrich Impacted the MYTH of Herd Immunity

Herd immunity, also called community immunity, is a hot topic.

The idea of obtaining herd immunity where we are all protected from sickness feels comforting and safe. It makes us want to rise up to protect others. The idea of falling short of the 95% vaccination rate said to be needed for herd immunity induces feelings of fear, uncertainty, and even anger at those we believe are preventing the protection of the herd. 

But what if the idea of herd immunity is not what we have always thought? 

When we refer to herd immunity today, it relates to the vaccination program and the percentage of children required to be vaccinated to protect the vulnerable. The history behind the theory of herd immunity, however, is different.

Herd immunity was an epidemiologic theory presented by A. W. Hedrich in 1933. He studied a community experiencing natural (wild) measles outbreaks from 1900 to 1931. His observations led him to conclude that when at least 55% of children under age 15 were infected with natural measles and recovered, the entire community experienced natural herd immunity. However, he also observed the cyclical nature of measles, and how the number of cases would be higher in some years and lower in others. 

Hedrich’s theory, based on observing wild measles cases, was then inappropriately applied to the vaccine program.

In 1967, the US Public Health Service predicted measles could be eliminated through vaccine-induced medical herd immunity. This prediction was based on the 55% infection rate in Hedrich’s natural herd immunity theory. The vaccination rate required for herd immunity started with his rate of 55%. But as it was found ineffective, the rate has steadily increased over the years. We are now told the childhood vaccination rate needed for medical herd immunity is around 95% for many vaccines. In addition, boosters continue to be added to the vaccination schedule in an attempt to increase their effectiveness. Increasing both the number of boosters and the vaccination rate are attempts to obtain herd immunity but seem to only provide further proof that the original theory of natural herd immunity based on wild measles cases does not apply to vaccinations.

News stories like the mumps outbreak on a U.S. Navy ship with a 100% vaccinated crew and numerous measles outbreaks in highly vaccinated schools only seem to weaken the case for vaccine-induced medical herd immunity.

Is it possible that herd immunity based on our vaccination program has given us a false sense of safety?

The real science simply suggests natural herd immunity happens when a community contracts and then recovers from wild infections, resulting in true, lifetime immunity. 

Additional Resources:

False Premise Of Medical Herd Immunity Drives Vaccination –

Dr. Suzanne Humphries: