Since the introduction of smallpox vaccine in the 19th century to the massive availability of influenza vaccines today, vaccines have helped millions of people develop immunity against some of the world's deadliest diseases.
With vaccines, many infectious diseases – such as smallpox and poliomyelitis – no longer exist outside US laboratories. Their lasting elimination has prompted researchers to develop new types of immunizations that can help people avoid other life-altering illnesses.
Here are six common diseases that no longer worry you about vaccines.
Smallpox exterminated thousands of people.
Smallpox is caused by the smallpox virus and can be easily spread by air. The disease causes a rash punctuated around the face and body of infected people, which turns into pustules that soften. Internally, the virus attacks the immune system, causing rapid death.
When European colonizers introduced smallpox to the American continent in the 17th century, it has become an epidemic, killing three out of ten people who have it.
In 1796, physician Edward Jenner discovered that people could become immune to smallpox if they were given an injection of a similar, less invasive virus strain. Jenner's experiments led to the development of the world's first vaccine.
In the next century, vaccinations became common practice in developed countries.
In 1972, the United States declared that smallpox had been eradicated. Less than ten years later, the World Health Organization announced that smallpox was the first disease to be eradicated from the world. It remains the only disease known to be 100% eliminated in the world.
Poliomyelitis leaves survivors with a permanent disability.
Poliomyelitis is a viral infection that lives in the throat and intestines of a person. One in four people who get the disease have flu-like symptoms that go away, but a smaller percentage suffer serious effects, including paralysis and respiratory failure.
Some infected children spent weeks inside giant appliances called steel lungs because polio prevented them from breathing on their own. According to NPR, 3,000 American children died of poliomyelitis in 1952 alone.
Deaths from polio were so common, in fact, that companies had taken out polio insurance for parents of newborns.
Poliovirus spread rapidly among the youngest populations as it was transmitted orally. This meant that it was easily transmitted to places such as public pools and daycares.
But once the vaccine was introduced in 1955, the rate of polio declined rapidly. In 1979, the disease was considered eliminated from the United States. The last case of polio reported in the United States dates back to the early 1990s. This patient contracted the disease abroad.
Today, the CDC recommends that American children receive four vaccines that will protect them for life against polio.
According to the World Health Organization, only three countries have active polio cases this year: Nigeria, Pakistan, and Afghanistan.
Diphtheria, a contagious bacterial infection, spread in the early 20th century.
Diphtheria infections affected more than 200,000 people in 1921 and caused about 15,520 deaths that year, according to the CDC.
Diphtheria initially causes sore throat, weakness and swollen glands in infected people. But then, a gray mucus begins to cover the back or the throat. If the bacteria spends enough time in the blood, the infection can produce toxins that can cause nerve damage and heart failure.
The disease spreads when an infected person sneezes, coughs or leaves saliva droplets on surfaces or objects. For this reason, people living nearby, especially in dense cities, were very susceptible to the disease in the early 1900s.
Since the diphtheria vaccine was introduced in the 1920s, natural epidemics have not been a problem for nearly a century in the United States. According to the CDC, fewer than five people across the country have caught the disease in the last decade. However, the disease remains common in some developing countries where people do not have access to vaccines.
The CDC recommends that children receive four doses of the diphtheria vaccine, followed by recalls every 10 years to provide complete protection.
Mumps causes children to develop painfully swollen faces.
Mumps is a respiratory disease caused by paramyxovirus. Like many other viruses, it spreads by contact with saliva. Before the advent of the mumps vaccine, about 186,000 people in the United States contracted the virus each year.
A person who catches mumps develops swollen and painful salivary glands. Swelling in the jaw area makes drinking difficult, which makes patients feel even weaker.
Mumps is not usually so lethal, but some patients have permanent complications such as hearing loss. About 20 to 30% of young men who develop the disease may develop swollen testicles, resulting in decreased sensitivity and fertility problems.
Mumps cases in the United States decreased by 99% after the introduction of the vaccine in 1967, and there are more than a few hundred cases a year.
Measles causes rash, high fever and serious long-term complications.
Measles (also called rubella) attacks the respiratory system and other organs. A person with the virus develops flu-like symptoms such as fever and runny nose, as well as a raised red rash all over the body.
If the infection is severe, it can lead to serious complications such as blindness, brain damage and even death.
It is estimated that 3 million people became ill each year in the late 1950s before the vaccine became available. Of this total, about 48,000 people have been hospitalized because of complications and about 400 to 500 people die each year.
Measles is very contagious: it can be transmitted when a person breathes the same air or touches the same surface as an infected person.
The disease can persist in a room for several hours after the departure of a sick patient. Since the onset of all symptoms may take a week or two, many people pass on the disease without knowing it.
The CDC announced that measles had been eliminated from the United States in 2000. Despite recent outbreaks, measles is completely preventable with the use of two-dose MMR vaccine, which also immunizes children against mumps and rubella.
Rubella causes brain damage and congenital anomalies in infants.
The symptoms of rubella (also called German measles) are similar to those of measles, although they are less severe. People who contract rubella usually develop a red rash, pink eye, and mild fever, although nearly 50% of those infected do not have any symptoms.
In 1964, nearly 12.5 million people in the United States contracted the disease. That year, nearly 11,000 women suffered from miscarriages or stillbirths related to the rubella virus. Children of infected mothers are born with cataracts, hearing disorders, developmental delays and heart defects.
Immunization against rubella became available in the late 1960s. The New York Times reported in 2015 that rubella had been eliminated from the Western Hemisphere.
The World Health Organization aims to eradicate the disease worldwide in the coming years.
This article was originally published by Business Insider.
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