Vaccination & Herd Immunity


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Vaccines are designed to protect individuals from dangerous infections, but they also have the added effect of conferring this protection to the wider community if enough people in that community are vaccinated. This effect is referred to as herd immunity, and in this article we look at herd immunity and how it benefits people of all ages.

The basis of herd immunity

Diseases are caused by a large variety of different living things broadly referred to as pathogens, and these include bacteria and viruses. These pathogens thrive by infecting a host body and abusing its resources and functions to allow them to reproduce and flourish. This action causes sickness, and a lot of the symptoms we see when are ill are either a direct consequence of the actions of pathogens or the result of our body’s defences trying to get rid of said pathogens.

One of the ways in which pathogens continue to flourish is by infecting another host and using their body to reproduce and spread even further. The term ‘contagious’ refers to pathogens that are especially good at spreading from person to person, and these are often a major concern and a target for vaccination because they can spread rapidly and affect entire communities.

The basis of herd immunity is that vaccines can limit the spread of pathogens from person to person, thereby protecting a large group of people even if some members of that group aren’t vaccinated. A person who has been vaccinated possesses an immune system (the term used for your body’s defence mechanisms) which is ready to quickly target and remove specific invading pathogens, and doing so prevents their spread.

What is herd immunity?

‘Herd immunity’ refers to the broader effects of vaccination on a community, and is achieved if enough members of a particular population have been vaccinated against a disease. As mentioned above, at this point a pathogen’s ability to spread is dramatically reduced to the point where it is very unlikely to spread from person to person, which in turn means that people who aren’t vaccinated now have some measure of protection against the disease.

How is herd immunity achieved?

Herd immunity is achieved by following immunisation or vaccination programmes. These are schemes devised by health authorities designed to provide enough vaccination to communities to achieve both individual protection against the disease and herd immunity. The latter is accomplished because, as mentioned above, if enough people receive vaccination against a condition, the pathogen responsible won’t be able to spread. 

What are the benefits of herd immunity?

Herd immunity dramatically reduces the spread of serious conditions that would otherwise be highly contagious. Examples include diphtheria, measles, and mumps amongst many others. The effects of vaccination programmes and herd immunity have achieved this to such a degree that some diseases have been completely eradicated from the world, and the best example of this is smallpox. Prior to the introduction of vaccination programmes smallpox was a major global problem, however, thanks to vaccination programmes and the effects of herd immunity, that is no longer the case.

Herd immunity can also offer protection to people who are, for medical or religious reasons, unable or unwilling to receive vaccination. People suffering from illnesses that compromise their natural defences are unable to safely receive vaccinations, and the reduced transmission and incidence of disease caused by herd immunity can spare them from severe sickness. Some groups object to vaccination on ethical or religious grounds, and these people also benefit from herd immunity.


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