If Herd Immunity is a thing, why should I vaccinate?


‘My child Abbey is coeliac, lactose intolerant, as well as being allergic to shellfish, coconut and anaphylactic to nuts. I am terrified of exposing her to something that might be directly harmful to her health. Besides, I heard that herd immunity means that she is protected anyway.’ – concerned mum.

When we have children that already suffer from relatively uncommon allergies, we tend to assume that they are the exception to every rule and the very thought of getting them immunised can become daunting and scary. In reality, the likelihood that a child like Abbey would have an allergic reaction to a vaccine is quite literally one in a million; the same probability that you will be struck by lightning within the next 12 months. Children’s immune systems are already dealing with millions of antigens (things like bacteria and viruses that trigger the body to produce antibodies) every day creating red flags ready for response on second exposure. Giving your child a vaccine is simply allowing them to red flag a few specific and nasty antigens; a process which is very natural and occurring all the time.


Figure 1Secondary Immune Response

The perception of risk, however is a powerful thing, and if the thought of giving your child a vaccine is causing anxiety because of their current health issues, please speak to your GP.

Regarding the rumours that herd immunity means that you shouldn’t need to vaccinate your child, be aware! The concept of herd immunity is a tricky one; it only works with a high vaccination threshold. If only a few scattered people in a population are vaccinated, it’s likely that if one person in that population contracts the disease, it will spread from person to person among those who are unvaccinated as their bodies have little to no ability to ward off primary infection. If, however, the opposite is true, and there are only a few scattered unvaccinated people in the population, the few that are unvaccinated are less likely to spread disease if it is contracted; buffered by the vaccinated population.


Figure 2Herd Immunity

In order to protect those in our community that are at serious risk of dying from infectious disease (the elderly, the immunocompromised and infants), a threshold of 95% total vaccination within the population of Australia needs to be achieved. Vaccinations are at an all-time high at the moment, with the ‘no jab no pay’ program, with vaccination levels sitting according to Figure 2  below:

Disease Herd Immunity Threshold (HIT)
Mumps 75–86%
Diphtheria 83–86%
Rubella 83–86%
Varicella (Chicken Pox) 90%
Pertussis (Whooping Cough) 92–94%
Measles 92–95%

Figure 3UNICEF. Herd Immunity Thresholds 


It is not, however until we maintain the 95% threshold rate that we can be sure that our vulnerable are protected. It is one thing to understand herd immunity and try to hide behind it, but we need to understand that by doing this we are putting the vulnerable at a serious risk.

The concept of herd immunity is further explained in the video below:

Herd immunity



  1. Centers for Disease Control. Possible Side-effects from Vaccines [Internet]. Atlanta, GA (USA): Centers for Disease Control; 2016 Dec [cited 2017 Feb 19]. Available from: https://www.cdc.gov/vaccines/vac-gen/side-effects.htm#mmr
  2. Centers for Disease Control. Vaccines when your child is sick [Internet]. Atlanta, GA (USA): Centers for Disease Control; 2016 Dec [cited 2017 Feb 20]. Available from: https://www.cdc.gov/vaccines/hcp/patient-ed/conversations/downloads/fs-child-sick.pdf
  3. Chen RT, Rastogi SC, Mullen JR, Hayes SW, Cochi SL, Donlon JA, et al. The vaccine adverse effect reporting system (VAERS). Vaccine [Internet]. 1994 [cited 2017 Feb 20]; 12(6):542-550. Available from: http://www.sciencedirect.com/science/article/pii/0264410X94903158
  4. World Health Organization. Global Health Observatory (GHO) data [Internet]. Geneva: World Health Organization; 2017 Jan [cited 2017 Feb 20]. Available from: http://www.who.int/gho/immunization/en/
  5. World Health Organization. What are some of the myths – and facts – about vaccination? [Internet]. Geneva: World Health Organization; 2017 Jan [cited 2017 Feb 20]. Available from: http://www.who.int/features/qa/84/en/



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