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SCIPAD - BIG IDEAS - BOOK 2
LIFE OF MICROBES
Vaccines and Smallpox
Smallpox is a serious, contagious, and often fatal viral disease.
Smallpox was responsible for an estimated 300 - 500 million
deaths during the 20th century. There is no effective
treatment for smallpox disease - the only effective measure
is vaccination.
One of the first people to experiment with vaccination
was Edward Jenner (1749–1823).
Cowpox is a viral disease that affects cows and the
people who milked them. Jenner noticed that people
who had recovered from cowpox never caught small
pox. Cowpox is similar to, but less serious, than smallpox.
Jenner suggested that infection with cowpox provides
protection against smallpox.
In 1796, Jenner decided to test this hypothesis:
1
He took some infected cowpox pus from an infected person
and inserted it into a cut in a young boy’s arm. The boy became sick with cowpox.
2
After the boy recovered from the cowpox illness, Jenner intentionally infected him with
smallpox by injecting pus from a smallpox lesion into his body.
3
The boy remained healthy due to his cowpox antibodies successfully preventing infection.
This became known as the world’s first vaccine (from the Latin for cow – vacca).
After an exhaustive worldwide vaccination campaign in the 19th and 20th centuries, the World
Health Organisation (WHO) announced the eradication of the smallpox virus in 1979.
Today, we live without fear of smallpox infection because of effect of vaccinations.
The smallpox virus is now present in only a few selective and highly secure laboratories to be used
for research purposes.
1. State Edward Jenner’s hypothesis.
2. Describe an observation Jenner made to support his hypothesis.
3. Suggest why the boy Jenner infected with smallpox did not develop the disease.
4. Where does the term ‘vaccine’ come from?
5. Do you think the cowpox and smallpox viruses are very similar?. Explain your answer.
6. (a) State the risk of smallpox infection in New Zealand today.
(b) Explain your answer to (a).
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