From the introduction of the smallpox vaccine in the 19th century to the mass availability of flu shots today, vaccines have helped millions of people develop immunity to some of the world’s deadliest illnesses.
Thanks to vaccines, many infectious diseases — like smallpox and polio — no longer exist outside of laboratories in the US. Their lasting elimination has spurred researchers to work to develop new types of immunizations that could help people avoid other life-altering diseases.
Here are six once-common diseases that you no longer have to worry about thanks to vaccines.
Smallpox used to wipe out populations by the thousands.
Smallpox is caused by the variola virus, and it can easily spread through the air. The disease causes a spotted rash around infected peoples’ faces and bodies, which turns into pustules that scab over. Internally, the virus attacks the immune system, causing rapid death.
When European colonizers brought smallpox to the Americas in the 17th century, it became an epidemic, killing three out of every 10 people who got it.
In 1796, physician Edward Jenner discovered that people could become immune to smallpox if they received an injection of a similar, less invasive strain of the virus. Jenner’s experiments led to the development of the the world’s first vaccine. Over the next century, vaccinations became a routine practice in developed countries.
In 1972, the US declared smallpox eradicated. Less than a decade later, the World Health Organization announced that smallpox was the first disease ever to be eradicated from the world. It remains the only disease recognized as 100% eliminated worldwide.
Polio leaves survivors with lifelong disabilities.
Polio is a viral infection that lives inside a person’s throat and intestines. One in four people who catch the disease develop flu-like symptoms that go away, but the rest suffer severe effects, including paralysis and respiratory failure.
Some infected children would spend weeks inside giant machines called iron lungs, since polio made them unable to breathe on their own. According to NPR, 3,000 US children died from polio in the year 1952 alone. Polio deaths were so common, in fact, that companies sold polio insurance to the parents of newborns.
The poliovirus used to spread rapidly among younger populations because it was transmitted orally. That meant it was easily transmitted in places like public swimming pools and day-care centers. But once a vaccine was introduced in 1955, polio rates declined rapidly. B 1979, the disease was considered eliminated from the US. The last reported case of polio in the US was in the early 1990s, and that patient contracted the disease abroad.
Today, the CDC recommends that children in the US receive four vaccines for lifelong protection against polio.
According to the World Health Organization, only three countries have active cases of polio 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 approximately 15,520 deaths that year, according to the CDC.
Diphtheria initially causes infected people to develop a sore throat, weakness, and swollen glands. But then a grey-colored mucus begins to cover the back or their throat. If the bacteria spend enough time in the bloodstream, the infection can produce toxins that cause permanent nerve damage and heart failure.
The disease spreads when an infected person sneezes, coughs, or leaves saliva droplets on surfaces or objects. For that reason, people living in close quarters, particularly in dense cities, were highly susceptible to the disease in the early 1900s.
The diphtheria vaccine was introduced in the 1920s, so natural outbreaks haven’t been an issue for nearly a century in the US. Less than five people in the entire country caught the disease over the past decade, according to the CDC. However, the disease remains common in some developing countries in which people don’t have access to vaccines.
The CDC recommends children receive four doses of the diphtheria vaccine, followed by booster shots every 10 years to ensure full protection.
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