Vaccines have changed the face of disease around the world. The World Health Organization (WHO) estimates that vaccines prevented 2 million childhood deaths in 2003, and the numbers continue to rise as vaccination supplies become available in developing countries. Vaccines often have a bad reputation because they can cause side effects, but even when someone does experience side effects, they're mostly mild -- serious reactions happen, but they're rare.
Most vaccines are given to children under the age of five, when they haven't yet had time to develop a strong immune system and are most vulnerable to infections. When we're vaccinated, our bodies react by creating antibodies against the particular virus or bacteria. If we're exposed to it later in life, those antibodies help us fight off the potential infection. We're not actually killing bacteria or viruses, we're taking ourselves out of play. Without vaccinations, we'd again be susceptible to a number of diseases. Here, we'll look at 10 vaccines that changed the world. Let's begin with the flu shot.
Influenza, the flu, is a viral infection that many people suffer seasonally. What you may not realize is that the flu is a serious illness, and it can pose life-threatening complications and death for some people. Every year, an estimated three to five million people around the world suffer from a severe form of the flu. Worse, 250,000 to 500,000 of them will die -- and those are just the estimates for industrialized countries [source: WHO].
While everyone should consider getting an annual flu vaccine, it's recommended that the elderly and the very young be vaccinated every year. This applies to people 50 or older -- especially those who live in nursing homes -- and kids between 6 months and 2 years old . Anyone with a chronic medical condition or weakened immune system should be vaccinated, as well.
If you're not one of the millions already getting your annual flu shot, this might make you reconsider: The influenza vaccine prevents an estimated 70 to 90 percent of flu infections.
In 1767, physician William Heberden made a distinction between smallpox and a new disease: chickenpox. Chickenpox is highly contagious, and although many of us associate it with childhood -- it's true that most cases occur in kids younger than 15 -- it can strike anyone at any age. For infants and people older than 15, chickenpox can be more complicated than a rash and flu-like symptoms. The older we are, the greater our risk for secondary infections and hospitalization.
If you've never had the chickenpox, the varicella vaccine is able to protect you from the virus about 70 to 90 percent of the time for about a decade. And if you do catch it, you'll have a milder case.
8. Human Papillomavirus (HPV)
Breast, lung, stomach, colorectal and cervical cancers are the most frequently diagnosed cancers among women around the world. Cervical cancer, specifically, has been linked to a sexually transmitted virus called human papillomavirus (HPV). There are more than 100 types of HPV infections: some cause warts (both common and genital) and some are considered high-risk types. It's these high-risk types that have been linked with cervical cancer, and they're implicated in oral and anal cancers, as well.
While many young women may become infected with the virus in their teens or 20s, their immune systems often are able to fight off the infections. Persistent high-risk HPV infections may lead to cervical cancer, a cancer that often doesn't develop until women are in their 30s or older. An estimated 300,000 to 500,000 women worldwide die from cervical cancer each year, and up to 85 percent of those deaths occur in developing countries. Annual gynecological checkups that include PAP smears help diagnose and monitor any cervical cell changes, but the only ways to prevent HPV infections are through abstinence and the HPV vaccine.
7. Hepatitis B
Hepatitis B is a virus that causes serious liver disease. In some people, hepatitis B virus (HBV) infections are mild, and even in more severe cases the body's immune system is able to fight it off. In others, the infection can become chronic, leading to liver cancer, liver scarring (cirrhosis) and liver failure. HBV is also highly contagious, and there is no cure. It can be prevented with a vaccine, introduced to the world in 1982. Since its introduction, Hepatitis B vaccinations have reduced infections by an estimated 75 percent [source: Centers for Disease Control and Prevention].
Hepatitis B is not the only form of hepatitis. There's also a vaccination for the hepatitis A virus, but no vaccine has yet been developed for hepatitis C.
6. Typhoid Fever
Typhoid fever is a disease caused by the Salmonella Typhi bacterium. It causes high fevers, weakness, headache, stomach pain and, sometimes, a spotty rash. Severe cases can be deadly. Although it's highly preventable, it continues to be a prevalent disease around the world. Infections in the U.S. are often contracted abroad -- the disease affects an estimated 21.5 million people living in developing countries [source: Centers for Disease Control and Prevention]. An estimated 30 percent of people who become infected die from the bacteria, but take note: Typhoid can be treated with antibiotics, and it can be prevented by boiling water, thoroughly cooking all foods and being vaccinated.
5. Diphtheria, Tetanus and Pertussis
Unlike many of the diseases we've been talking about, diphtheria, tetanus and pertussis (whooping cough) are caused by bacteria, not viruses. Diphtheria affects the throat, thickening it to the point where it can become difficult to swallow. Tetanus causes muscles to tighten, which can lead to a sufferer's inability to open and close his or her jaw. Pertussis causes coughs so severe it's difficult to breathe. All three conditions can develop severe complications, including death.
The vaccine for diphtheria, tetanus and pertussis, called DTaP (Tdap for adults), is a trivalent vaccine, immunizing us against all three diseases in one vaccination. Recently, hepatitis B and HiB vaccines have been combined with the DTaP vaccine to create a pentavalent vaccine, one that protects against five different diseases.
If you don't have children, you might not know about rotavirus, an infection that causes severe diarrhea, vomiting and fever, and can lead to dehydration. Rotavirus is responsible for a half a million deaths every year and millions of hospitalizations. It's estimated that by the age of five, almost every child worldwide will suffer from a rotavirus infection. There's no cure for rotavirus, and treatment usually consists of fluids and allowing the disease to run its course, which takes about three to eight days.
In 2006, however, a vaccine to prevent rotavirus was introduced to the world. Studies have since shown that it prevents infections in roughly 85 to 98 percent of immunized children [source: Parashar].
3. MMR: Measles, Mumps and Rubella
Measles, mumps and rubella (also known as German measles) are all deadly viral diseases that were once common illnesses. Without immunization, serious cases of these diseases can lead to grave complications. Measles, for example, can cause pneumonia, seizures, brain damage and death. Mumps can turn deadly, as well, and can cause deafness, secondary infections and swollen ovaries or testicles. A pregnant woman exposed to rubella has an increased risk of miscarriage, and the fetus has an increased risk of developing birth defects.
One shot of the MMR (measles, mumps, rubella) vaccine, which is a trivalent vaccine, is effective 95 percent of the time, and a second dose is given to boost that number to 100 percent. Worldwide, between 2000 and 2008, deaths from measles infections dropped by 77 percent [source: Bill & Melinda Gates Foundation].
Polio is a virus that can cause permanent paralysis, and among those stricken with paralysis, about 5 to 10 percent will die from respiratory paralysis complications [source: Centers for Disease Control and Prevention]. When the polio vaccine was introduced in the U.S. in 1955, it quickly made a big impact. Infections dropped from about 20,000 a year in the '50s to just 10 in 1979 [source: Centers for Disease Control and Prevention]. Today, polio has been eradicated from the Western hemisphere as well as the European and Western Pacific areas of the world.
There are two types of polio vaccines. One is given orally (oral polio vaccine or OPV) -- this is the original vaccine -- and one is a shot (inactivated polio vaccine or IPV). The oral vaccine is used around the world, to great success -- in 2008, only four countries continued to be endemic.
Smallpox has been around since, well, we're not sure when. It's been dated possibly back as far as 10,000 B.C., killing populations around the world in epidemic after epidemic. There's no cure for smallpox, and the virus that causes it, the variola virus, kills about 30 percent of the people it infects. It can disfigure, scar and blind those who survive.
There is good news, though. Worldwide smallpox eradication was declared in 1980, all due to the success of the smallpox vaccine and global immunization efforts. In 1972, Americans were no longer vaccinated against the virus, and by 1986, no countries continued to immunize against smallpox.
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