This article has been updated.

Every minute, six lives are saved by vaccines, according to the World Health Organization (WHO), while up to 5 million deaths a year are avoided because of them, says UNICEF. Once-fatal diseases like smallpox have been eliminated and others are largely kept in check with vaccines. But how did this lifesaving breakthrough come about?

The idea of using cells from infectious diseases to stimulate the human body’s immune system to fight them is not new: people were using basic forms of immunization centuries ago, as the timeline below shows.

But the remarkable success of vaccines has not been without its challenges – one of the main ones being misinformation and anti-vaccination sentiment, which can be traced back to the 1850s when smallpox immunization became mandatory in the UK.

As we mark World Immunization Week, which this year reminds people that 'For every generation, vaccines work', let’s look back at some of the milestones in the remarkable journey to a vaccine-protected world.

Early forms of vaccinations

As early as the 1500s, people were using simple forms of vaccinations to create immunity from smallpox, according to Gavi, the global vaccines alliance.

At around the same time, Lady Mary Wortley Montagu, a smallpox survivor and wife of the British ambassador to Turkey, had her three-year-old son inoculated in the city and returned home to promote the benefits of vaccination.

The first modern vaccination

But it was not until 1796 that British country doctor Edward Jenner studied the effects scientifically. Noticing local rural communities that were exposed to cowpox seemed to be immune to smallpox, Jenner first inoculated a child with cowpox matter and then, two months later, injected the same boy with smallpox matter.

It worked, and historians now refer to it as the first modern vaccination – named after vaccinia, the Latin name for cowpox. Despite its success, the public took a while to come on board, with some even worried that it would turn them into cows. With further testing and evidence of its efficacy, the smallpox vaccine spread to other continents until mandatory vaccination programmes came into effect in Britain and parts of the US during the 1840s and 1850s. The disease was declared eradicated by the WHO in 1980.

Laboratory-produced vaccines

Perhaps best-known today for inventing a method of preserving milk, Louis Pasteur discovered a vaccine against chicken cholera in 1879 after a vial of the virus was mistakenly left open to the elements for a month. Chickens injected with the neglected virus became ill but recovered swiftly.

Pasteur reasoned that the virus had weakened, or attenuated. His accidental discovery opened the door to producing vaccines in the laboratory by creating a less potent form of a virus that would stimulate immunity without harming the patient.

Pasteur went on to develop successful vaccines against anthrax and rabies. In 1885, Spanish doctor Jaime Ferrán created a human cholera vaccine. And in 1896, British and German scientists developed a vaccine against typhoid.

20th-century vaccines

The 1900s witnessed a huge growth in vaccine discovery. The 1920s saw the creation of vaccines against tuberculosis, tetanus and diphtheria. In 1938, South African virologist Max Theiler and his team created a vaccine for yellow fever – Theiler later won a Nobel Prize for his discovery, the first time it had been awarded for a vaccine.

Polio had become one of the most feared diseases in the world during the late 19th and early 20th centuries, with outbreaks killing thousands of people. In 1953, US scientist Jonas Salk created an inactivated polio vaccine, which he first tested on himself and his family. A success, the vaccine was licensed in 1955 and, two years later, cases of polio in the US had dropped from 58,000 to 5,600.

It was also a period in which combination vaccines were introduced – DTP (diphtheria, tetanus and pertussis or whooping cough) in 1948 and MMR (measles, mumps and rubella) in 1971.

The COVID-19 revolution

After the COVID-19 pandemic was confirmed in March 2020, work began on vaccines at astonishing speed and, within 12 months, new vaccines were being tested and approved. The previous fastest vaccine turnaround was six years for mumps.

The speed was the result of groundbreaking previous work on vaccines for HIV, MERS and SARS, which used genetic material to stimulate cells to produce “spike proteins” which create antibodies to fight a virus.

When COVID-19 vaccinations were rolled out globally in 2020-2021, it marked the first time mRNA vaccines had been approved for widespread use. One study estimates the number of lives saved as a result of the various COVID vaccines at 2.5 million. Despite this, there is evidence that confidence in vaccinations more generally has gone down since the pandemic.

The future of vaccinations

The COVID-19 vaccine paved the way for more mRNA vaccines, including most recently, a vaccine to protect against a potential bird flu pandemic.

Researchers are discovering new ways to vaccinate, too. A team at Stanford University has recently tested a "universal vaccine" on mice with positive results. Instead of training the immune system, as vaccines have traditionally done, this new type of vaccine mimics how immune cells communicate with each other. If it successfully translates to humans, a single nasal spray could protect against all coughs, colds and flus, reports the BBC.

The question that the COVID-19 pandemic, in particular, laid bare is – will everyone have access to future vaccines? For Gavi, the focus is on ensuring that no one is left behind when it comes to tackling preventable diseases.

Latest data reveals that lower-income countries contributed over $300 million towards immunization programmes in 2025, a new record and a sign that immunization is being prioritized in national budgets.

“In an increasingly constrained global financing environment, countries are stepping forward to play a lead role in securing the future of immunization,” said Gavi CEO Dr Sania Nishtar. “Record co-financing at this scale demonstrates that the shift toward country-led, sustainable immunization systems is gaining momentum and that we are entering a new era when it comes to protecting children against preventable diseases.”