Question

(3 pts.) The concept of herd immunity applies to:

All infectious diseases

All contagious diseases

All infectious and all contagious diseases

Neither all infectious nor all contagious diseases

Answer 1

The concept of herd immunity applies to: Neither all infectious nor all contagious diseases

It can not protect against all the contagious disease, whereas it implies to a particular contagious disease against which vaccination is done for example, if someone with measles is surrounded by people who are vaccinated against measles, the disease cannot easily be passed on to anyone, but it will not be able to protect a population from invasion of a new infection from any other contagious diseases such as rubella, pertussis, chickenpox.

A contagious disease is one that is spread directly from person to person. When a high percentage of the population is vaccinated, it is difficult for infectious diseases that are also contagious to spread, because there are not many people who can be infected. For example, if someone with measles is surrounded by people who are vaccinated against measles, the disease cannot easily be passed on to anyone, and it will quickly disappear again. This is called ‘herd immunity’, 'community immunity' or 'herd protection', and it gives protection to vulnerable people such as newborn babies, elderly people and those who are too sick to be vaccinated. Herd immunity does not protect against all vaccine-preventable diseases. The best example of this is tetanus, which is infectious but not contagious. It is caught from bacteria in the environment, not from other people who have the disease.