Herd Immunity

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What is Herd Immunity?

In 1933 Dr AW Hedrich put forward a theory based on his observations of the community that he had lived in for the previous 30 years. He noted that if 68% of the community caught measles by natural infection, the other 32% of the community appeared to be protected and did not catch the measles. This theory was called “Herd Immunity” and that is all it is, a theory. It was made before there were any vaccines for measles, based on the population catching the wild measles virus, not on a population being injected with the measles vaccine virus and it has never been proven since in either an unvaccinated or vaccinated population.

The World Health Organisation (WHO) also states, “Herd immunity theory proposes that, in diseases passed from individual to individual, it is difficult to maintain a chain of infection when large numbers of the population are immune.” Please note that the WHO says “theory” and “proposes”, so it is not a fact, it is only a speculation or hunch based on observations (definition of theory) that was put forward for discussion and consideration (definition of propose). Also observe that the WHO are saying this applies when a disease is passed from one individual to another as in one person catching the disease and infecting another, nothing about vaccinations. In fact there are studies showing that even when regions have a 99% uptake of the measles vaccine, measles as a disease still exists. So this would suggest that vaccines do not confer herd immunity at all.

Please understand that there are two form of herd immunity:

  1. Natural Herd Immunity
  2. Vaccine/artificial Herd Immunity.

Natural/Wild Herd Immunity

  • Mothers who have experienced natural/wild infection of childhood illnesses such as measles, mumps, rubella and chickenpox, pass on to their children strong, naturally acquired antibodies via the placenta and breastfeeding.
  • This protects infants when they are at there most vulnerable, one to six months of age, and until they can acquire their own lifelong immunity by experiencing the childhood illness at the appropriate time.
  • Exposure to the full bacteria or virus which the body can recognise
  • Correct antibody response and duration of response; IgG 1 & 3; cell mediated immunity
  • TH1 dominant response, activated T cells
  • Immunity is usually lifelong

Vaccine/Artificial Herd Immunity

  • Mothers who have been vaccinated and not experienced the childhood infection pass on a weaker protection to their children
  • The children are more vulnerable to infections
  • Exposure to parts of the bacteria and genetically modified viruses, which the body does not automatically recognise
  • Excessive and incorrect antibody response; IgG 2 & 4; decrease in cell mediated immunity
  • TH2 dominant response, antibody only response and no cell mediated response
  • Immunity wanes in 2-10 years

Measles, mumps, rubella and chickenpox (varicella zoster virus-VZV) were regarded as typical infections of childhood until very recently, they are normally clinically mild and result in lifelong immunity (link). It is also known that the immunity conferred by vaccines is of short and unknown duration. So this is creating a problem because the more children that do not catch these diseases in childhood the more adults who are likely to catch them later on in life when any immunity they may have had wears off; and while these diseases are mild in children they are not in adults. Indeed mumps in adult males can cause sterility.



Hedrich, A. W. “MONTHLY ESTIMATES OF THE CHILD POPULATION ‘SUSCEPTIBLE’ TO MEASLES, 1900-1931, BALTIMORE, MD.” American Journal of Epidemiology 17.3 (1933): 613-636.

Global Manual on Surveillance of Adverse Events Following Immunizations. World Health Organization, 2014. Print.

Epidemiological analysis of immunity against vaccine-preventable diseases: rubella, measles, mumps and chickenpox. National Center for Biotechnology Information/National Library of Medicine / National Institutes of Health.


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