About vaccines

What are vaccines?

Vaccines are designed to trigger an immune response to a certain virus or bacteria that would usually cause disease. Current vaccines contain a small portion of a killed or weakened organism or a protein from the outer coating of the virus or bacteria. After the vaccine is given, the body remembers how it fought the weakened version, and when it encounters the real disease, it fights the disease more rapidly.

How are vaccines made?

Depending on the type of organism and the disease it causes, vaccines are designed using a variety of strategies:


Viruses can be weakened or inactivated so that they trigger the immune response, but no longer cause disease. Weakened viruses can still reproduce, but not fast enough to cause an infection, and inactivated viruses are chemically treated so they cannot reproduce at all.

Measles, mumps and chickenpox vaccines are made by weakening the virus, whereas polio, hepatitis A, influenza and rabies vaccines use inactivated virus.


Bacteria that cause disease by producing a toxic protein can be neutralised by inactivating the toxins with a chemical. Diptheria, tetanus and whooping cough vaccines are made this way.

Subunit vaccines use a small harmless compound from the bacteria to produce an immune response, instead of using the whole bacterium. Some subunit vaccines use the sugar coat that bacteria use to enter the body, or a crucial protein that the bacteria needs to function. Pneumococcal and meningococcal vaccines are made using this method.
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