As the world awaits the imminent arrival of one — or several — COVID-19 vaccines, many people may wonder how important vaccines actually are to safeguarding public health. In this feature, we answer that question by looking at what vaccines have done for us throughout history.

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This photograph shows a doctor using a jet injector gun during mass smallpox immunization procedures in 1972.
Image credit: Smith Collection / Gado / Getty Images.

Researchers who have looked at trends of vaccine acceptance around the world have found that, overall, people’s trust in vaccine safety and effectiveness has been on the rise over the past few years.

However, they have also expressed concern that the race for a COVID-19 vaccine may have triggered more hesitancy among certain groups.

Speaking at this year’s WIRED Health:Tech conference, Prof. Heidi Larson, from the London School of Hygiene & Tropical Medicine, in the United Kingdom, noted that “Because of the hyper-uncertainty and the whole environment of trust and distrust around the COVID vaccine, there are groups that have gotten together to resist” upcoming vaccination.

Many may now be wondering why researchers are so keen on vaccines — and whether vaccines have really achieved much for public health.

So, in this Special Feature, we look at some key moments in vaccine history and how vaccines have revolutionized public healthcare.

Article highlights:

Vaccines work by exposing the immune system to a very small amount of a virus or “information” about a virus — enough to “teach” it to recognize and react to that pathogen.

The idea of exposing the body to a virus in a controlled way to “train” it to prevent infection is by no means a modern conception.

Already in the 1500s, Chinese and Indian physicians practiced inoculation against the variola virus, which causes smallpox.

Some accounts from China in the 1600s suggest that doctors attempted the inoculation by grinding up smallpox scabs and blowing them into the patient’s nose through a silver tube.

In Europe, inoculation against smallpox, a process known as “variolation,” was introduced and popularized by Lady Mary Wortley Montagu in the early 18th century.

Lady Wortley Montagu was the wife of the British ambassador to the Ottoman Empire. From 1716–1718 she travelled across Europe to Constantinople, present-day İstanbul, where she learned about variolation.

She was so impressed by the evidence of its effectiveness that she submitted her own son for inoculation against the smallpox virus while in Constantinople and continued to advocate for the procedure on her return to Britain.

In a letter to a friend, Lady Wortley Montagu praised the procedure:

“The small-pox, so fatal, and so general amongst us, is here entirely harmless by the invention of ingrafting, which is the term [that the Ottomans] give it. There is a set of old women who make it their business to perform the operation every autumn. […] Every year, thousands undergo this operation… There is no example of anyone that has died in it; and you may believe I am well satisfied of the safety of the experiment.”

The word “vaccine” entered circulation soon after, when British physician Edward Jenner started experimenting with different ways of inoculating against variola.

In 1796, Jenner discovered that exposing people to small quantities of the cowpox virus, called “vaccinia” or the “vaccine virus,” was safer than exposing them to the variola virus that infects humans. The cowpox virus was also effective in preventing smallpox.

Thus, inoculation against the “vaccine virus” eventually became the umbrella term that we use today: vaccination.

This discovery was truly revolutionary for public healthcare worldwide, given the disastrous effects that smallpox had been having for centuries.

The World Health Organization (WHO) call smallpox “one of the most devastating diseases known to humanity,” as it caused millions of deaths worldwide over some 3,000 years.

Smallpox was officially eradicated in 1980, thanks to consistent global programs of vaccination. On May 8 of that year, the 33rd World Health Assembly made the historical announcement: “The world and all its peoples have won freedom from smallpox.”

According to the WHO, in the 20th century alone, smallpox ended the lives of around 300 million people.

The WHO and national health authorities everywhere have also made strides toward ending the threat of other contagious diseases, many of which often spread fast among children.

Measles, mumps, and rubella (MMR) are three of the most contagious diseases among humans and are capable of causing epidemics if left unchecked.

While it is unclear when, exactly, the measles virus started spreading, researchers believe that it has been around for hundreds of years, causing hundreds of thousands of infections and thousands of deaths, up until the 20th century.

The first vaccine for measles was only introduced in 1963, and an improved version became available in 1968.

According to the European Centre for Disease Prevention and Control, thanks to the measles vaccine, the number of related deaths worldwide decreased by 73% between 2000 and 2018. The vaccine prevented an estimated 23 million deaths during this period.

The first vaccine for mumps appeared in 1948, though it only produced short-lived immunity against the virus. An improved vaccine appeared in 1967, and it is still used today.

According to the Centers for Disease Control and Prevention (CDC), “Mumps was a frequent cause of outbreaks among military personnel in the prevaccine era, and [mumps] was one of the most common causes of aseptic meningitis and sensorineural deafness [deafness caused by damage to the auditory nerve] in childhood.”

In the United States alone, at least 186,000 cases of mumps appeared each year before the start of a national vaccination program in 1967.

“Since the [two-dose MMR] vaccination program was introduced in 1989, U.S. mumps cases decreased more than 99%, with only a few hundred cases reported most years,” the CDC report.

The first rubella vaccine appeared in 1969, and it was developed by the same researcher who had improved on the measles and mumps vaccines: the American microbiologist Maurice Hilleman. A safer, more effective rubella vaccine became available in 1979.

Thanks to consistent national vaccination programs, rubella and congenital rubella syndrome were eliminated in the Americas in 2016.

The U.K. has also eradicated rubella, in 2015, and measles, in 2016. Other countries are still working to eliminate these viruses.

At present, children can receive the MMR vaccine, which protects against all three of these viral illnesses. Healthcare providers administer it in two doses, one at 12–15 months of age and another at 4–6 years.

Another vaccine that has made a monumental difference to world health is the DTP, or DTaP, vaccine. It protects against diphtheria, tetanus, and pertussis — whooping cough — and children receive the vaccine in five doses.

Diphtheria can cause breathing difficulties, heart failure, and paralysis, leading to death in some cases.

A vaccine for diphtheria first became available in the 1920s, after the illness had caused millions of deaths among children. In 1921 alone, Corynebacterium diphtheriae, the bacterium behind the disease, reportedly caused 206,000 cases of diphtheria and 15,520 related deaths.

Thanks to widespread vaccination, however, global cases have dropped to a minimum, and diphtheria has become “nearly unheard of” in the U.S., according to the CDC.

Tetanus, also known as lockjaw, commonly produces spasms and tightening of the jaw muscles, which can lead to further health problems.

Since the popularization of childhood immunization against tetanus in the 1940s, cases have been decreasing at a steady rate, the CDC observe.

“The death-to-case ratio has declined from 30% to approximately 10% in recent years,” the CDC report, adding that “An all-time low of 18 cases (0.01 cases per 100,000) was reported in 2009.”

Whooping cough is caused by the bacterium Bordetella pertussis, and it can cause severe symptoms in people of all ages. The main symptom is coughing fits that can cause breathing problems.

The disease has been around at least since the 16th century, and in the U.S., more than 200,000 cases appeared annually before the introduction of widespread immunization in the 1940s.

Since then, thanks to vaccinations, the incidence has reportedly decreased by more than 80%.

Finally, the “humble” flu shot has been preventing hundreds of cases of severe illness year after year. According to the most recent data from the CDC, flu vaccines “prevented an estimated 58,000 flu-related hospitalizations” in the U.S. in 2018–2019.

Flu jabs have also prevented severe symptoms and events in people with existing chronic conditions, such as heart disease and chronic obstructive pulmonary disease, known as COPD.

According to the WHO, “We now have vaccines to prevent more than 20 life-threatening diseases” to help safeguard every human being’s right to health.

Researchers are constantly working to increase that number, so that one day, everyone has the best chances of staying healthy for longer.