History of vaccines

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Across more than two centuries, vaccines have evolved from simple observations into highly engineered and safe medical technologies. What began as the observation-based study of disease within local communities has grown into a field driven by laboratory innovation, molecular biology, and big data.

However, what has remained constant is the goal: to prepare the immune system in advance of coming into contact with infectious diseases - safely, effectively, and at scale.

1^st Vaccine – 1700s (1796)

Vaccination began with observation. Across Africa and Asia, communities had already tried to foster protective immunity against the deadly disease of smallpox by inoculating themselves with small amounts of infectious matter. The method worked but remained risky.

In 1796, English physician Edward Jenner developed a safer method of immunisation when he investigated local claims that milkmaids who had contracted cowpox rarely developed smallpox.

He tested this idea by introducing material from a cowpox sore into his gardener’s son and then tested the protective effect with smallpox inoculation. The result was that the boy had a markedly lower reaction to the smallpox virus.

Jenner’s discovery led to the first ‘vaccine’ – named after the Latin Vacca for cow! A simple but powerful idea was formed: exposure to a less dangerous form of a disease can train the body to fight a more dangerous one.

Attenuated vaccines – 1870s

By the late 19th century, vaccine development moved from clinical observation to scientific experimentation. Inspired by Jenner’s cowpox model, French microbiologist Louis Pasteur showed that pathogens could be deliberately weakened – or attenuated -  in the lab so they no longer caused severe disease but still triggered immunity.

He developed vaccines for chicken cholera, anthrax, and, in 1885, rabies. This was the first live attenuated viral vaccine. Pasteur’s discoveries marked a turning point and led to the development of vaccines for many diseases.

Inactivated vaccines (1890s)

Scientists soon explored another approach: instead of weakening pathogens, why not kill them entirely?

In the 1890s, researchers surrounding German microbiologist Robert Koch showed that components – antigens – from heat or chemically inactivated bacteria could still stimulate immunity.

The breakthrough led German and British researchers to develop new inactivated vaccines against notorious diseases like typhoid, which were soon widely used in military settings.

The idea was simple… even a non-living pathogen can teach the immune system to respond.

Toxoid Vaccines – (1920s)

But not everything is so easy.  Some diseases cause harm to people through the toxins they produce.

During the 1890s, German microbiologist Emil Behring had already used antibodies from the blood serum of inoculated horses to neutralise toxins released by diphtheria bacteria.

During the 1920s, French veterinarian Gaston Ramon drew on Behring’s Nobel-prize-winning research when he demonstrated that these toxins could also be inactivated, creating ‘toxoids’, which safely triggered protective immunity.

Parallel research also led to the identification of adjuvants, such as alum salts, which are substances that enhance the body’s immune response.

By the end of the period, powerful and safe vaccines had been developed for many formerly deadly bacterial – and some viral – diseases.

Viral vaccines – 1940s

In the decades following the Second World War, advances in cell culture and egg-based production made it possible to grow viruses safely and at scale. This enabled the development of vaccines for several major viral diseases.

Polio became a defining example. Vaccines developed in the mid-20th century were distributed globally, sometimes administered on sugar lumps - a simple method that supported mass immunisation campaigns and has become symbolic of the time.

More and more states began to develop and sponsor routine immunisation schedules for their populations. Meanwhile, international efforts to control the spread of diseases such as yellow fever led to the rollout of new vaccination certification and passport schemes.

Subunit vaccines – 1960/70s

Scientists and companies continued to try to improve the effectiveness and safety of existing vaccines and develop vaccines for new diseases. Instead of using whole pathogens, they focused on using smaller ‘sub-cellular’ or ‘subunit’ components that could trigger an immune response.

Beginning in the late 1960s, several new subunit vaccines were developed for bacterial and viral diseases ranging from typhoid to hepatitis B.

1980s biotech breakthroughs also meant that it became possible to use harmless engineered microbes rather than the pathogens themselves to produce subunits.

During this time, a growing number of vaccines began to be offered as combinations to reduce the number of vaccination appointments.

Nucleic acid vaccines – 2000s

Increasingly sophisticated bioengineering methods laid the ground for the next generation of nucleic acid vaccines. Instead of delivering part of a pathogen, these vaccines deliver genetic instructions that tell the body how to produce a harmless piece of it.

This approach allows for rapid design and adaptation. Much of the groundwork for these vaccines was laid during the 1990s and 2000s.

Between 2020 and 2021, the rapid global development and rollout of nucleic acid vaccines during the COVID-19pandemic launched a new genomic era of vaccine innovation.

Future vaccines

Looking to the future, anything is possible! Vaccines are no longer only about preventing infectious disease. Researchers are now exploring vaccines that treat and prevent conditions such as cancer or that are tailored to individuals.

New tools, including computational modelling and advanced trial designs, are changing how vaccines are discovered and tested, especially during outbreaks.

As these technologies evolve, they continue to redefine both the scope and the speed of vaccine development. However, the underlying principle of teaching our own immune system how to recognise and counter threats remains unchanged.

References

https://www.chop.edu/vaccine-education-center/science-history/vaccine-history/developments-by-year

https://assets.publishing.service.gov.uk/media/61fab1bae90e0768a4477f4f/UKHSA-vaccine-timeline.pdf

https://www.who.int/news-room/spotlight/history-of-vaccination/a-brief-history-of-vaccination

https://www.immunize.org/vaccines/vaccine-timeline/