How do vaccines work?
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Explainer Video
Summary
How do vaccines work?
In a nutshell
Vaccines are administered to protect against infections and severe illnesses caused by pathogens. They stimulate an immune response that produces protective antibodies. The immune system has a memory and can produce protective antibodies if it faces that pathogen again.
Vaccination
Definition
Vaccination is the introduction of a small amount of an inactive or dead form of a pathogen into the body to protect us from disease.
Vaccinations are usually given to children and vulnerable people as well as people who are going to travel to countries where there is a risk of a serious disease. Vaccines can be given by injection, orally or as a nasal spray.
Examples
MMR vaccine | Protects against measles, mumps and rubella |
HPV vaccine | Protects against Human papillomavirus. |
COVID vaccine | Protects against COVID-19. |
Method of action
As well as containing an inactive or dead form of a pathogen, vaccines also contain chemicals that tell your immune system to respond. Lymphocytes then produce antibodies against the pathogen, but as the pathogen is dead or weakened, we don't actually become ill.
This ensures that if we ever get infected with a 'live' version of the pathogen, our immune system has memory and can protect us from the infection immediately.
| 1. | The vaccination stimulates the immune system. |
| 2. | Lymphocytes detect antigens from the dead or inactive pathogen and produce a specific antibody against it. Antibodies bind to the antigen. |
| 3. | Lymphocytes remember the antigen of that specific pathogen. |
| 4. | Infection by the pathogen. |
| 5. | The lymphocyte recognises the antigen and produces many specific antibodies. These antibodies bind the pathogens and cause them to be killed before they can make you really ill. |
Herd immunity
If a large proportion of the population is immune to a pathogen, the spread of it is reduced and it is difficult for the pathogen to spread to the unvaccinated. This is known as herd immunity. Due to the success of vaccination, the WHO (World Health Organisation) declared that smallpox had been completed eradicated worldwide in .
A. | Unvaccinated but still healthy |
B. | Vaccinated |
C. | Unvaccinated and infectious |
| 1. | No one in the population is vaccinated, and the spread of infectious diseases is high. |
| 2. | Some of the population is vaccinated, but the infectious diseases have still spread. |
| 3. | The majority of the population is vaccinated, and the spread of infectious diseases is contained. |
Booster vaccines
Some viruses frequently mutate into new strains. This means they are less recognisable to lymphocytes. This is why certain vaccines are regularly updated so the immune system has protection against new strains.
Example
The flu vaccine is updated every year.
Whilst some antibodies give lifelong protection, like those produced after a measles vaccine, others do not. This is because after a period of time the antibody levels fall below the threshold needed for immunity. Boosters are administered to increase antibody levels again.
Example
COVID-19 antibody levels are reduced after six months, this is why a booster is administered.
FAQs - Frequently Asked Questions
What is herd immunity?
If a large proportion of the population is immune to a pathogen, the spread of it is reduced and it is difficult for the pathogen to spread to the unvaccinated, this is known as herd immunity.
Why do I need a booster vaccine?
After a period of time the antibody levels fall below the threshold needed for immunity. Boosters are administered to increase antibody levels again.
How do vaccines work?
Vaccines are administered to protect against infections and severe illnesses caused by pathogens. They stimulate an immune response that produces protective antibodies.
What is vaccination?
Vaccination is the introduction of a small amount of an inactive or dead form of a pathogen into the body to protect us from disease.