Learning Team

Vaccines have a history of making a difference

An empty syringe lies sideways in front of a variety of glass vials

Throughout human history, disease outbreaks have had an immense impact on almost every aspect of human life. Well-known outbreaks include the Black Death in the Middle Ages, the Spanish flu of 1918, HIV in the 1980s, Ebola in Central and West Africa between 2014 and 2016, and the Zika virus in Brazil, Central America, the Caribbean and the United States in 2015–2016. 

During each of these health emergencies, regardless of when they occurred, officials looked for ways to contain the disease and mitigate illness and death rates. This included isolating (or ostracizing) those who were experiencing the illness; using specialized equipment (e.g., the plague doctor’s mask), restricting travel, contact tracing and the use of quarantine.  

Interestingly, many of these health measures go back for hundreds of years. For example, “the first known quarantine was enacted in Ragusa (city-state of Dubrovnik) in 1377, where all arrivals had to spend 30 days on the nearby island of Lokrum before entering the city” (Huremović 2019).  

In modern times, and during the current pandemic, contact tracing, handwashing, mask wearing and quarantining have all been used to diminish the transmission of the COVID-19 virus. However, unlike Byzantine or medieval times, there are now greater medical options available to deal with disease, and this includes the use of vaccines. How, then, do vaccines work and when were they invented?  

The World Health Organization (WHO) explained that our immune system has thousands of antibodies that recognize and remove foreign substances (antigens) in our bodies to ensure our good health. However, “when the human body is exposed to an antigen for the first time, it takes time for the immune system to respond and produce antibodies specific to that antigen” (WHO 2020). Vaccines are designed to help bolster the body’s ability to develop immunity to antigens.  

According to the Centers for Disease Control and Prevention, “Vaccines help develop immunity by imitating an infection. This type of infection, however, almost never causes illness, but it does cause the immune system to produce T-lymphocytes and antibodies.”  

In plain language, vaccines help our bodies recognize and react to foreign substances, such as viruses, to remove them from the body before severe illness or death can occur. In addition, where enough people are vaccinated, a herd immunity to specific diseases is achieved and the chains of transmission for the disease are broken. The percentage of the population that is needed to achieve herd immunity varies from disease to disease, but when enough people are vaccinated, the disease will eventually be eradicated.  

Like quarantines, vaccines have been around for hundreds of years, as has variolation — the building of immunity by infecting patients with a less virulent form of a disease. The earliest documented trials of variolation were aimed at treating small pox in China and India in the 16th century. Variolation was done either by rubbing infected pus onto an uninfected person’s skin or blowing the dried pox into their nose. 

In many cases, the infected person would develop a mild form of small pox, making survival much more likely if they contracted the disease again. The death rate of those who were not inoculated was recorded to be approximately 30 per cent, while those who were exposed to the virus through variolation had a death rate between one and two per cent.  

By today’s standards for immunization, these techniques were rudimentary, maybe even a bit gross, but they give rise to the notion that by exposing a person to a disease in a small way, an immune response can be triggered and helpful in the event the person is fully exposed to the disease. 

Eventually, the practice of “buying the pox” to use as a means of inoculating a person against small pox migrated from China and India to Africa and Europe. However, the invention of the first vaccine is credited to British doctor Edward Jenner in 1796.  

Jenner noticed that milk maids, who often contracted cow pox on their hands, did not develop small pox. That observation led to Jenner injecting the pus from cow pox lesions into a cut made in a young boy’s arm. After six weeks, Jenner exposed the boy to small pox. The child did not develop small pox in the first or subsequent exposures.  

Of course, Jenner’s experiment would not be allowed today — strict ethical procedures prevent this sort of risk to participants — but his work was foundational to the development of small pox vaccines. By 1980, vaccination worldwide allowed the WHO to declare that the small pox disease had been eradicated.  

Since the development of the small pox vaccine, several other vaccines have been developed. Rabies, whooping cough, polio, measles, mumps, diphtheria, tetanus and chicken pox are all diseases for which there are vaccines.  

Developments in medical science, improved standards of living and sanitation, including vaccinations, have increased life expectancies in Canada. The Canadian Encyclopedia wrote “The most dramatic improvements in mortality have resulted from reductions in infant mortality and a consequential increase in life expectancy. In 1931, the number of years a person could expect to live at birth was 60 years for males and 62.1 for females. By 2014, life expectancies had risen to 79.7 years for men and 83.9 years for women, accounting for an average life expectancy of 81.8 years.”  

While there is not one single factor that explains the dramatic rise in life expectancies in Canada, vaccines and vaccination have played a clear role, paving the way to better health outcomes and longer lives.


Boylston A. 2012. “The Origins of Inoculation.” Journal of the Royal Society of Medicine 105: 309–313. 10.1258/jrsm.2012.12k044 (accessed March 4, 2022). 

Centers for Disease Control and Prevention (CDC). 2018. “Understanding How Vaccines Work: The Immune System—the Body’s Defense Against Infection.” CDC website. https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html (accessed March 4, 2022).  

Hussain, A., S. Ali, M. Ahmed and S. Hussain. 2018. “The Anti-vaccination Movement: A Regression in Modern Medicine.” Cureus 10(7), e2919. https://doi.org/10.7759/cureus.2919 (accessed March 4, 2022). 

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Keenan, G. 2020. “A Brief History of Vaccines and How They Changed the World.” World Economic Forum, April 9. https://www.weforum.org/agenda/2020/04/how-vaccines-changed-the-world/ (accessed March 4, 2022). 

Saleh A., S. Qamar, A. Tekin et al. 2021. “Vaccine Development Throughout History.” Cureus 13(7), e16635. DOI 10.7759/cureus.16635 (accessed March 4, 2022).  

World Health Organization (WHO). 2020. “How Do Vaccines Work.” WHO website. https://www.who.int/news-room/feature-stories/detail/how-do-vaccines-work (accessed March 4, 2022).