Lesson 5

How vaccines were discovered and developed

Learning outcomes & key terms

  • Students will be able to explain how vaccines were discovered.
  • Students will understand the difference between a vaccination and variolation.
  • Students will know the scientists who were involved in the discovery of vaccines.
  • Students will understand how scientific method has over time as knowledge has developed.


Variolation: inoculation of material from the pocks of variola (smallpox); an instance of this.

Vaccination: Treatment with a vaccine to produce immunity against a disease.

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About vaccination

Many diseases that were once killers are now eradicated due to the high efficiency of vaccines.

Until recently most people have taken for granted life without having their daily routines such as where they are going, what they are doing and who they are meeting impacted by an outbreak of disease.


Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body’s adaptive immunity they help prevent sickness from an infectious disease (Wikipedia).


Vaccination is the administration of a vaccine to help the immune system develop protection from a disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results. The effectiveness of vaccination has been widely studied and verified. Vaccination is the most effective method of preventing infectious diseases. Widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the elimination of diseases such as polio and tetanus from much of the world (wikipedia).


Variolation or inoculation was the method first used to immunise an individual against smallpox (Variola) with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. The procedure was most commonly carried out by inserting/rubbing powdered smallpox scabs or fluid from pustules into superficial scratches made in the skin. The patient would develop pustules identical to those caused by naturally occurring smallpox, usually producing a less severe disease than naturally acquired smallpox. Eventually, after about two to four weeks, these symptoms would subside, indicating successful recovery and immunity (Wikipedia).

Smallpox – A Case Study

Interest into smallpox started as long ago as 1000 AD when the Chinese started inoculating to prevent further spread of the disease. They would collect diseased cells from an infected person and then dry them out by carrying the cells in their pocket. They would then scratch a healthy persons arm and place some dried cells in.

Skip forward to 1545 and there was an epidemic in India. Up to 8000 children died.

The process the Chinese used became known as variolation. Variolation became very popular between 1706 and 1721.

In 1721 Lady Mary Montagu called for variolation for her 2 year old daughter. Not everyone agreed with the process of variolation.. The results, however, were sometimes fatal: two to three percent of those variolated died of smallpox (in contrast to 20-30% who died after contracting smallpox naturally).

Unfortunately those who were variolated still had enough active disease to infect others. (Not the best way to defend against disease).

In 1770 real progress was made into annihilation of Smallpox. Edward Jenner (1749-1823), an English doctor, learned from a milkmaid that she believed herself protected from smallpox because she had caught cowpox from a cow.

Cowpox is an uncommon illness in cattle, usually mild, that can be spread from a cow to humans via sores on the cow. During an infection, dairy workers may have pustules on their hands. Sufferers can spread the infection to other parts of the body.

We know now that the cowpox virus belongs to the Orthopox family of viruses. Orthopox viruses also include monkeypox virus and variola viruses, which cause smallpox.

Whilst Jenner had ideas about how to vaccinate it wasn’t until 1796 that he tested his hypothesis on a 8 year old boy with great success. This test lead to the vaccine that we have today and is still one of the most successful vaccines around. “To finish the story in 1855 Laws were passed to allow vaccination and by 1980 The World Heath Organisation declared Smallpox completely eradicated.

The Stars of Immunisation

Edward Jenner

Edward Jenner is known as the Father of Immunology. and is famous for his discovery of smallpox vaccine. This was the first successful vaccine ever to be developed and remains the only effective preventive treatment for the fatal smallpox disease.

Edward Jenner was born on May 17, 1749, in Berkely, Gloucestershire, England. He died of a stroke in 1823.

Jenner wasn’t always met with adoring fans. In 1802 a caricature appeared of Jenner treating patients and those around him sprouting cattle like appendages. It was here that fears started to emerge about vaccinations.

During the eradication of Smallpox there always had to be a last patient- Ali Maow Maalin was exposed to the disease on October 12, 1977. Ali came into contact with the disease and developed a fever. When he was first diagnosed he was told he had chickenpox and sent home. When it was finally obvious that he had smallpox he kept it to himself and didn’t go into isolation. He came into contact wtih 91 people during his illness.

The WHO (World Health Organisation) took precautions to stop any re-kindering of the disease. They did a massive search and found all 91 people. No-one got sick and two years after watching the area carefully Smallpox was declared gone.


Louis Pasteur

Louis Pasteur furthered the concept through his work in microbiology. His experiments spearheaded the development of live attenuated cholera vaccine and inactivated anthrax vaccine in humans (1897 and 1904, respectively). 

In the 1870s, he applied his previous method of immunizing chickens against chicken cholera to anthrax, which affected cattle and thereby aroused widespread interest in combating other diseases with the same approach. In May 1881, Pasteur performed a famous public experiment at Pouilly-le-Fort to demonstrate his concept of vaccination. He prepared two groups of 25 sheep, one goat and several cows. The animals of one group were twice injected, with an interval of 15 days, with an anthrax vaccine prepared by Pasteur; a control group was left unvaccinated. Thirty days after the first injection, both groups were injected with a culture of live anthrax bacteria. All the animals in the non-vaccinated group died, while all of the animals in the vaccinated group survived. The public reception was sensational.

Class activity

Part 1

  • You will work in groups of 3.
  • You will create a slide on one of the topics below (decided by your teacher).
  • Each member iof the group try a different summarising method (using the methods that follow) and present the information on one slide.
  • Find pictures that represent your findings for another slide (method 2).
  • The finished slides (2 in total – one info and one graphic) should then be printed off and arranged in order for the class to see.


Method 1

  • Delete unwanted extra (trivial) details that can go without losing the overall sense
  • Delete information that is repeated in some way
  • Replace the details with more general terms or descriptions
  • Select a topic sentence or create 1 if it is missing
  • Check there is sufficient detail to make sense

 Method 2

Create a visual representation of key aspects of the information such as a table, chart, flow diagram or spider diagram. Try to show the relationships between pieces of information where you can.

Method 3 

Skimming – preview the information on the factsheet by highlighting the important information. Then focus on the headings and subheadings to write a short written summary of the factsheet.


1. Variolation – 900-1000

  • What is variolation?
  • Who discovered and used it in this time period?
  • Was it effective?
  • What where the dangers with this method?

2. Lady Montegu – 1700’s

  • How did Lady Montegu contribute to the spreading the of variolation?
  • How was this method different to previous variolation methods?
  • Was it effective?
  • What where the dangers with this method?

3. Edward Jenner – 1796

  • Explain how Edward Jenner discovered the smallpox vaccination.
  • When was smallpox officially eradicated from the world?
  • Was it effective?
  • What where the dangers with this method?

4. Variolation & Vaccination – 1840

  • England bans variolation and only vaccination is allowed.
  • What is the difference between variolation and vaccination?
  • Why do you think variolation was prohibited in favour of vaccination?

5. Louis Pastuer – 1880 & 1881

  • Pasteur accidently discovers the vaccine for chicken cholera.
  • Describe how he made this discovery.
  • Pasteur developed and publicly demonstrated his anthrax vaccine.
  • How did he convince his peers that his vaccine worked?