Herd immunity is a term used to describe an ability to rely on the majority of a population being vaccinated against preventable diseases in order to protect the remaining vulnerable minority who are unable to have their own immunity to specific community-carried preventable diseases. Their inability to be immune themselves is usually due to either being unable to safely or completely receive vaccinations themselves – such as babies – or having extensive health issues which increase their susceptibility for disease and/or prevent the safe administration of vaccinations, such as the frail or very sick. Vulnerable parties include newborns, the elderly, the immuno-suppressed or the seriously ill.

A very simple example is if you consider 10 people in a room, 9 of which are vaccinated for measles, and one unvaccinated newborn. The 9 vaccinated parties are unable to carry and transfer the measles virus to the newborn, despite the newborn’s lack of vaccination, as the newborn is protected by the “herd”.

In addition to the instance of newborns, whereby they haven’t yet been vaccinated against some diseases – or received their full course of necessary vaccinations to be deemed immune due to age – some people are born with a complete inability to be vaccinated at all. Some children and adults suffer from genetic, inherited immuno-deficiency. They are unable to be vaccinated by no choice of their own. Immuno-deficiency such as Primary Immune Disease (PID) mean these people are born with an inability to produce immunogloblins required to fight off certain diseases, rendering them immuno-suppressed for life.

An example of people who depend entirely on herd immunity for their protection can be seen in the story of Sonia Bychkov Green, mother of four boys – all of which have PID. They look like ordinary, “normal” boys – just as any child or person within your community may appear. As Sonia explains: “It’s literally what prevents my kids from getting sick”.

Other people acquire their immuno-suppression through certain diseases, such as HIV and AIDS, or through medical treatments, such as chemotherapy, which weakens their immunity while they are treated for their health conditions. People who are seriously ill often cannot safely receive vaccines themselves and thus rely on herd immunity to protect themselves from their conditions being worsened through contracting preventable diseases.

In order for herd immunity to work a significantly high percentage of the population needs to be adequately vaccinated and deemed immune in order to prevent those most at risk from catching the diseases. This means the responsibility to protect the vulnerable, susceptible members of a society belongs to those with an ability to vaccinate themselves, and their children. The onus of ensuring immuno-suppressed adults and children do not face significant health risks – or even death due to preventable disease strains – lies with all of us who are capable of safely receiving a vaccine.

A great demonstration of how diseases are spread and can be prevented with adequate herd immunity is shown in this animated video from Vaccines Today:
Being conscious of the vulnerable and susceptible members of the community around you should be enough of a reason to ensure you responsibly, pro-actively vaccinate. If it was your child, your family member or friend who was the vulnerable person, you too would hope the community around you would take it upon themselves to protect them from contracting an unnecessarily risky, possibly even life-threatening, and most importantly preventable, diseases.