How vaccines work

Vaccines work by stimulating our immune system to produce antibodies without actually infecting us with the disease.

Vaccines trigger the immune system to produce its own antibodies against disease, as though the body has been infected with it. This is known as active immunity.

Newborn babies are already protected against several diseases, such as MMR, because antibodies have passes into them from their mothers via the placenta. This is known as passive immunity.

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How are vaccines made?

The first step to make the organism (called the pathogen) that produces the disease. 

The pathogen is a virus or a bacterium.

Viruses and bacteria can be mass produced in the laboratory by infecting cells grown in tissue culture. 

The pathogen must then be altered to ensure that it doesn't trigger the disease itself. This can be done by:

  • Weakening, or 'attenuating', it by growing it repeatedly to select a strain that's less dangerous - MMR vaccines are attenuated.
  • Taking out the part of the pathogen that causes the immune response and using this in the vaccine - The Hib vaccine is made this way.
  • Using the toxin that the pathogen makes and inactivating it - The tetanus vacine is produced in this way.

The treated pathogen is then combined with other ingerdients, such as stabiisers and preservative, to produce a dose of vaccines.

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Can you overload a child's immune system?

There might be a concern that too many vaccines at a young age could 'overload' a child's immune system. This isn't the case. Studies have shown that vaccines do not weaken a child's immune system.

As soon as a baby is born, they come into contact with a huge number of different bacteria and viruses every day, and their immune system copes well with them.

The bacteria and viruses used in vaccines are weakened or killed and there are far feer of them that the natural bugs that babies and children come into contact with.

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How long does a vaccination programme work?

  • When a vaccination programme is introduced, everyone in the population of a certain age or risk group is offered a specific vaccine to tr to reduce the number of cases of the disease. 
  • Vaccination programmes aim to protect people for life. They often concentrate on young children, as they're the most vulnerable to many potentially dangerous infections. Some vaccination programmes are targeted at older people or certain task groups. 
  • When a vaccination programme against a disease begins, the number of people catching the disease goes down. But as the threat recedes, it's important to keep vaccinating, otherwise the disease can start to spread again.
  • If enough people in a commuity are vaccinated, it's harder for a disease to pass between people who have not been vaccinated. This is called 'herd immunity'.
  • Heard immunity is particularly important in protecting people who can't get vaccinated becuase they're too ill, or they are having treatment that damages their immune system.
  • The Department of Health and the Health Protection Agency (HPA) record the vacciantions that people have each year.
  • The HPA also records the number of cases of each disease each year.
  • This way, the HPA can work out the impact that each vaccination has on a particular disease.
  • This data helps the Joint Committee on Vaccination and Immunisation onsider whether the routine vaccination programme neess to be changed.
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Eliminating disease

As more and more of the population is vaccinated, the disease can sometimes dissapear completely and the vaccination programme can be stopped, as has happened with smallpox.

The more infectious the disease, the greater the number of people who have to be vaccinated to keep the disease under control.

Measles, for instance, is highly infectious. If vaccination rates go down, measles will quickly spread again.

It is known that at least 90% of children have to be immune in order to stop the disease from spreading. If 95% of children are protected by MMR, it's possible to eliminate not just measles, but mumps and rubella as well.

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