In the UK, young people are vaccinated against a range of different diseases. A vaccination introduces small quantities of dead or inactive forms of a pathogen into the body. As the pathogens are dead or inactive, it does not cause disease.
Introducing the pathogen to the body stimulates the white blood cells to produce antibodies that are complementary to the antigens on the surface of the pathogen.
During this process, memory cells form and can remain in the blood for a long time. Vaccination acts as a primary infection, so when the patient has a second exposure to the pathogen, white blood cells quickly produce the right antibodies. This produces a more rapid response to a secondary infection.
Although, vaccination and immunisation are often used interchangeably they have different meanings. Vaccination is the act of receiving a vaccine, whereas immunisation is the process of becoming immune through vaccination.
Vaccinations make a patient immune to a certain disease. The individuals are protected against it before they have been infected.
There are two types of immunity:
A benefit of active immunity is its long-lasting protection. When the person is exposed to the disease in the future, the immune system produces antibodies to combat it. However, active immunity can take several weeks to develop.
Although passive immunity provides a more immediate effect, its protection only lasts for weeks or months.
Vaccinating a large number of the population against serious diseases will reduce the likelihood of unvaccinated people getting infected by those specific pathogens. This is known as herd immunity.
Three main scenarios take place with herd immunity:
1. A large number of the population are not vaccinated – If a few people become ill and contagious, the disease will spread rapidly because most people are not immune.
2. A minority of the population are vaccinated, while the majority are not – If a few people become ill and contagious, the disease will spread to fewer people because the vaccinated people will remain healthy and many unvaccinated people will remain healthy.
3. Most of the population are vaccinated – If a few people become ill and contagious, the disease will be unable to spread to most people because they are immune. The few unvaccinated people will be unlikely to come in contact with an infected person.