Vaccination: From Early Experiments to Eradication

One of the key moments in medicine was when vaccination was discovered. It became possible to protect people from deadly diseases.

Smallpox was a disease that killed about 60% of the people who caught it. Before the vaccine, inoculation had been in use for centuries and reduced chances of dying. The way it was done was neither scientific or greatly effective as it involved the transfer of pus from one person with smallpox to others in order to try and immunise them.

Smallpox vaccine

[photo: James Gathany CDC]

A Short History of Vaccination

Edward Jenner, an English scientist, is credited with the discovery of vaccination. He wasn’t the first to work on it, but he was the one who made the well-publicised breakthrough. Instead of using smallpox to create the immunity, he used the related disease, cowpox. Why? He knew that milkmaids were immune to smallpox and he believed that this was because they had been exposed to cowpox.

Cowpox is a lot like smallpox but much milder and non fatal. So during a smallpox outbreak, Jenner used pus taken from the hands of a milkmaid suffering from cowpox and applied it to the arms of his gardener’s son. The boy did not catch smallpox.

During the 19th century, the technique was improved and developed. For example, the French scientist Louis Pasteur developed vaccines for the deadly disease anthrax (caused by the rod-shaped bacteria Bacillus anthracis) and rabies (caused by a virus). As scientists gained a better understanding of how vaccination works, during the 20th century it became possible to vaccinate against many more diseases — measles, mumps and polio, for example.

How Vaccination Works

A vaccine produces a weak form of the target disease in your body which is easy for your immune system to deal with. This stimulates your body’s immune system to produce antibodies – cells in the bloodstream that destroy invading bacteria, viruses or toxins (poisons). These ‘invaders’ are collectively known as antigens.

Once your immune system has developed the antibodies, it remembers them and can produce them when needed.  Each antibody is specific to just one type of antigen, which is why you need different vaccines for each disease.

There are different ways of producing these antibodies:

1. Use a vaccine made from the dead antigen. Your immune system will detect these but does not know whether they are active or not and will manufacture the antibodies to get rid of them anyway. This type of vaccine usually requires a periodic booster to maintain immunity.

2. Use a vaccine made from the live antigen, but weakened or inhibited in some way so that it reproduces more slowly. This gives your body time to create the antibodies without you becoming ill. The antigens continue to reproduce after the time of the vaccination so will require a booster less often.

3. Use a vaccine made from a de-toxified form of the poison that causes a disease.

4. Use a vaccine made from parts of a virus (e.g. the protein outer coating) that provoke the immune system to respond. These are less successful as it can be difficult to mimic the exact shape and size of the target virus.

Bird flu vaccine.

[infographic: US National Institutes of Health]

Eradication of Diseases Through Vaccination

The World Health Organisation (WHO) declared all out war on smallpox in the aim of eliminating it completely. Thanks to a massive worldwide effort, this was achieved by 1977. No one in the world catches smallpox any more. They have declared the same war on polio and are getting close to success.

Taught science for 16 years at a secondary school in the East Midlands.