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Smallpox and the story of vaccination

Published: 25 April 2019

Smallpox and vaccination are intimately connected. Edward Jenner developed the first vaccine to prevent smallpox infections, and this success led to the global eradication of smallpox and the development of many more life-saving vaccines.

Key facts about vaccination

  • Smallpox vaccination is based on a thousand-year old technique called inoculation, in which a small sample of infected matter is deliberately introduced into the body in order to prevent the full disease from developing. 

  • A vaccine stops you from getting an infectious disease by stimulating your body's immune system to produce chemicals called antibodies that will combat a future infection.

  • The first vaccine was developed to protect against smallpox, a deadly disease that killed thousands of people until the 1800s. Thanks to vaccination, smallpox was completely eradicated in 1979.

  • An antitoxin is a blood-based product that 'borrows' immunity from another person or animal to help you fight an infection, once you already have it.

  • The sciences of microbiology and immunology have produced different vaccines and antitoxins to prevent and combat a range of infectious diseases.

For a long time people observed that you rarely get the same infectious disease twice, or if you do it’s usually much milder the second time round.

What if you could artificially expose a person to a safer form of the disease before they encountered a potentially lethal version of the full disease? That might prevent them getting the full-blown disease if they encountered it in the future. This is the basis of vaccination, which itself is based on the thousand-year-old practice of inoculation.

Vaccination has saved millions, mostly children, from many potentially fatal diseases.

What is vaccination?

Vaccination is a medical technique that uses the body’s own immune system to protect it from infectious diseases.

A vaccine introduces a weakened or inactive version of the infection into the body. The person’s immune system reacts to the vaccine by producing antibodies (molecules in the blood that attack and destroy the infection).

Once someone has been vaccinated they are immune, which means that if they encounter the actual disease their body can fight off the infection before the disease takes hold.

Inoculation, or how to use the disease against itself

The first attempts to produce immunity artificially were recorded in China approximately a thousand years ago.

Healthy people would inhale a powder made from the crusts of smallpox scabs in order to protect themselves from the disease. They might show mild symptoms, but they were usually resistant to any subsequent exposure. The practice was called inoculation.

Another version of inoculation involved inserting powdered scab or pus from a smallpox pustule into a scratch on the skin made by a sharp instrument.

Inoculation was practiced in Asia and parts of Africa. It reached Europe and America via traveller's tales and experiences in the 1700s, where it was also called variolation, after the Latin name for smallpox—variola.

Two thorns used for smallpox inoculation, Palestine, 1921.
Science Museum Group Collection More information about Two thorns used for smallpox inoculation, Palestine, 1921.

Cotton Mather, an American churchman, was told about inoculation by his enslaved worker, Onesimus  who had been inoculated as a child in Africa. In 1721, Mather campaigned for inoculation during an outbreak of smallpox in Boston and met with some success—but also much hostility.

Lady Wortley Montagu, wife of the British ambassador to Turkey, observed the scratch method of inoculation in Constantinople at seasonal inoculation ‘parties’. On returning to Britain, she had her children inoculated during a smallpox outbreak in 1721. She introduced the practice to London Society and even King George II had his children inoculated.  

Inoculation was an uncertain procedure and people sometimes developed the full-blown disease or inadvertently spread it to others while they were still infectious.

Edward Jenner and the smallpox vaccine

Smallpox was a highly infectious disease that was endemic around the world. The disease began with a fever and a red rash that spread all over the body. After a few days the rash turned into opaque pustules that formed scabs. The scabs fell off, often leaving deeply pock-marked skin.

In about 5–10% of cases (72% among children) a malignant form of smallpox was fatal. This is why people were so willing to inoculate their children. 

The English physician Edward Jenner (1749–1823) inoculated patients at his Gloucestershire practice.

Edward Jenner, 1838.
Science Museum Group Collection More information about Edward Jenner, 1838.

In the surrounding countryside, he noticed a similar practice among local farming communities.

Milkmaids, who were renowned for their clear complexions, were often immune to smallpox and its scarring pock marks.

Their work brought them into contact with cowpox, a mild disease of cattle that only left a single pustule on the hands of people who milked the cows.  

Locals who were aware of this phenomenon began to inoculate themselves with the cowpox pustule as a way to ward off the more deadly smallpox. 

The hand of Sarah Nelmes infected with the cowpox.

Jenner decided to test the effectiveness of this practice. In 1796 he took some matter from a cowpox pustule on the hand of milkmaid Sarah Nelmes and injected it into the arm of a young boy called James Phipps.

James developed a scab and experienced some soreness and mild fever for a day. Six weeks later, Jenner inoculated young James with smallpox matter and the boy showed no signs of the disease.

Jenner published his findings in a short treatise. He called the procedure vaccination after the Latin word for cow (vacca). Despite some opposition, vaccination soon replaced the riskier variolation and in 1853, 30 years after Jenner’s death, smallpox vaccination was a standard practice for preventing smallpox.

Today people can get vaccines against a whole host of infectious diseases, but smallpox is not one of them. Thanks to a global eradication programme of mass vaccination, the entire world population was officially free of this life-threatening disease by 1979.

Six lancets, steel and tortoiseshell in a shagreen and silver case, as used by Edward Jenner.

More about this object

The science behind vaccination

Louis Pasteur Science Museum Group Collection
Louis Pasteur

Clinical practice proved Jenner’s vaccine successful, but neither he nor anyone else knew why it worked. An explanation had to wait for the science of bacteriology to develop at the end of the 1800s.

The French scientist Louis Pasteur (1822–1895) believed that germs (microorganisms) were responsible for infectious diseases such as smallpox. He tested his 'germ theory of disease' on anthrax, an infectious disease of people and animals.

Through his microscope, he identified a microorganism in infected blood, which he believed was responsible for the disease. Pasteur developed a solution containing a weakened form of the bacteria, which he could use as an inoculating agent. He was able to measure the success of his experiment by the absence of bacteria in the inoculated host.

Pasteur called the process vaccination in honour of Jenner’s work on smallpox, and vaccination became the generic term for the technique.

The difference between antitoxins and vaccines

Both vaccines and antitoxins are derived from toxoids, modified bacterial toxins that stimulate protective antibodies in the blood. Antitoxins are used as a treatment or cure when the infection is already present in the person. Vaccines, on the other hand, are examples of prophylactics - they prevent a disease from developing by stimulating the body's immune system to produce antibodies in the blood.

If a person has a disease, their immune system is already overwhelmed by the infection so a vaccine wouldn't help. Antitoxins work by harnessing the immunity of another person or animal to boost the immune system of the infected person.

Bottle of diptheria antitoxin Science Museum Group Collection
A bottle of diphtheria antitoxin developed by Emil Adolf Behring in 1891.

Antitoxins were developed by two researchers, Shibasaburo Kitasato (1852-1931) and Emil von Behring (1854-1917), who inoculated guinea pigs against diphtheria so they were immune to the disease. They then isolated a serum from the blood of the immunised animals and used it to treat guinea pigs that already had diphtheria. They found that the serum cured the sick animals of the disease. 

Antitoxins are made by collecting and purifying serum from animals (usually horses) inoculated with a non-lethal dose of disease toxin. Like vaccines, there are specific antitoxins for specific diseases, and the same technique is used for manufacturing treatments for other toxins such as snake venom.

Because antitoxins are not manufactured in the patient’s own blood, their effect only lasts a few weeks. This is enough to treat the disease if you already have it, but it doesn’t prevent you from getting it again. 

Vaccines don’t treat a disease, but prevent it from happening by stimulating the host to produce their own immunity, which can last for years.

Opposition to vaccination

In the 1800s, some people objected to compulsory vaccination because they felt it violated their personal liberty. The Vaccination Act of 1853 introduced mandatory smallpox vaccination in England and Wales for infants up to three months old. The Act was met with opposition from people who demanded the right to control their bodies and those of their children.

The Anti Vaccination League and the Anti-Compulsory Vaccination League formed in response to the mandatory laws, and numerous anti-vaccination journals sprang up. After a visit to New York, in 1879, by prominent British anti-vaccinationist William Tebb, The Anti-Vaccination Society of America was founded.

Despite the opposition to vaccination by some, smallpox was completely eradicated from the world 100 years after the Anti-Vaccination League was set up.

The significance of herd immunity

When a high percentage of the population is protected through vaccination, it becomes difficult for a disease to spread because there are so few susceptible people left to infect. This is called herd immunity.

Herd immunity is crucial for protecting people who cannot be vaccinated, such as babies and people with compromised or ineffective immune systems.

In several countries, reductions in the use of some vaccines have been followed by increases in the number of cases of potentially lethal diseases, as herd immunity begins to break down. People can lose confidence in a vaccine for a number of reasons.

In the mid-1970s, a report from the Great Ormond Street Hospital for Sick Children in London alleged that 36 children suffered neurological conditions after having the DTP (Diphtheria, Tetanus and Pertusis) vaccine. Television documentaries and newspaper reports drew public attention to the controversy.

As a result, uptake of the DTP vaccine in the UK fell from 81% to 31%, and whooping cough (pertusis) epidemics followed, leading to the deaths of several children.

Public confidence was only restored after a national study identified every child between 2 and 36 months hospitalized in the UK for neurological illness, and determined that the risk was very low. DTP vaccine uptake eventually increased to levels above 90%, and disease incidence declined dramatically.

Vaccination gives public health authorities something of a conundrum. When they succeed in vaccinating almost all of their communities, herd immunity kicks in and the incidence of a disease decreases. But if the next generation then has no memory of the trauma and danger of that disease, then public attention can shift from the significant risks in having the disease to the much lower risks from being vaccinated.

Suggestions for further research

  • Edward Jenner, An inquiry into the causes and effect of the Variole Vaccinae, 1798
  • Herve Bazin, The Eradication of Smallpox, 2000
  • Gareth Williams, Paralysed with Fear: The Story of Polio, 2013
  • Robert Gaynes, Germ Theory: Medical Pioneers in Infectious Diseases, 2011

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