Vaccination and
Herd Immunity


Ben Janaway

  
Vaccination is a subject of media controversy, either hailed as  a miracle prevention of disease or a shortcut to ‘autism’. Although the benefits of vaccination are well evidenced, the pseudoscientific misconceptions around the process persist. In this work I hope explain more clearly how and why vaccination works, as well as to dispel unhelpful myths that run the risk of reversing decades of work and placing people at risk.

How does vaccination work

Vaccination is the process of introducing a dead or ‘attenuated’ (weakened) form of a bacteria or virus in to the human body, with the aim of ‘training’ the body to recognise the disease. Surface markers on the cells of bugs are often recognised by the body after a short period of infection, which means the body can readily target the invader if met a second time.  This immune recognition is part of our innate (self-existent) defence (the other parts including non-specific fever and inflammation.)

Use of weakened or dead forms means that we can gain the cellular memory without the risk of severe infection. This is akin to using a ‘flight simulator’ before stepping into the cabin. Some vaccines are life long, others require boosters.

Vaccinations such as Measles, Mumps and Rubella are incredibly effective at removing infection risk and are common place in the western world. Polio, small pox and others have been almost completely eradicated by the same methods.

Herd Immunity

Herd immunity is a term used to define the proportion of the population that must be ‘immune’ to a bug to prevent spread. If you imagine that a bug is 5% contagious, then you would have to meet 20 people to infect one with it. If the bug can only exist for a short time, the chances are it will not live to infect another. By ensuring enough people are vaccinated, the chances of spreading a low virulence bug to a susceptible host (i.e unvaccinated, elderly, very young) becomes negligible.

This is why mass vaccination is so important.  Herd immunity breaks the  chain of hosts needed for the bug to survive and spread. 

Resurgence and myth

Resurgences of measles in high population areas are due to people refusing to have their children vaccinated for fear of side effects or suspicion of maleficence. Reasons vary, but include allegations of an increased risk of autism, mercury poisoning or financial trickery. All without basis. 

Avoiding vaccination puts you, family members and the public at risk. Associations of vaccines with ‘autism’ are false and have been disproved scientifically. As well as these claims being scientifically and pragmatically nonsensical, the ethic quandary of misleading the public cannot be ignored.  To date, all research suggests that vaccines are safe.

Any opinions above are the author's alone and may not represent those of the NHS or Mind and Medicine. Any comment is based on the best available evidence at the time of writing.  All data is based on externally validated studies unless expressed otherwise. Novel data is representative of sample surveyed. Online recommendation is no substitute for seeing your own doctor and should not be taken as medical advice.
 
Sources

https://emergency.cdc.gov/agent/smallpox/
https://www.vaccines.gov/basics/protection/
http://www.nhs.uk/conditions/polio/Pages/Introduction.aspx
https://www.cdc.gov/vaccinesafety/concerns/autism.html
http://www.nhs.uk/Conditions/vaccinations/Pages/How-vaccines-work.aspx