Vaccination
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Vaccination means giving someone a substance that makes an immune system reaction. The immune system is the way a body fights infection. The immune system's reaction makes someone less likely to get that infection.
If the vaccinated person get exposed to the virus or bacteria that causes the disease, the person will fight it and not get sick.
Another word used for vaccination is immunization. These words mean things that are a little different. Vaccination is when a person is given something to make the immune system learn to fight an infectious disease. Immunization is when a persons immune system learns to fight an infection. Immunization can happen from vaccination. But immunization can also happen from getting the infection. For example, a person can be immune to hepatitis B if he gets sick with hepatitis B. After a person gets hepatitis B and then gets well, he is immunized from getting it again. A person can also be immunized from to hepatitis B by taking the hepatitis B vaccination.
So vaccination and immunization have meanings that are a little different. But when people say these words, they usually mean the same thing. People say immunization to mean the same thing as vaccination.
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[change] Where vaccination comes from
The first use of the term "vaccine" is credited to Louis Pasteur. The word is derived from the Latin vacca, meaning cow. A virus that mainly affects cows (Cowpox) was used in the first scientific demonstration that giving a person one virus could protect against a related and more deadly one.
[change] History of vaccination
The first vaccination ever was for smallpox. In 1796 an English doctor, Edward Jenner noticed something. He saw that people who got cowpox did not get sick from smallpox. He gave a young boy the cowpox virus to protect him from smallpox. This was done by scratching liquid from cowpox sores into the boy's skin. This same method using liquid from sores was also used to give people smallpox. People did this so they might get smallpox on one place on their body. Then they could pick which body part got scars from smallpox. But sometimes people who did this got very sick from smallpox. Some even died. This was a dangerous thing to do. But people did it because it was less dangerous then getting smallpox.
Edward Jenner gave the boy cowpox in the same way people tried to give smallpox. Six weeks later, he scratched smallpox into the boy's skin. The boy did not get sick from smallpox. This boy was the first person ever to get a vaccination.
It was not until almost 100 years after the smallpox vaccination that medicine found the next vaccination. In 1879 the vaccine for cholera was found. Since then vaccines for 28 different diseases have been found.
[change] Herd Immunity
Herd immunity is an important part of how vaccines work. A herd is a group of animals. Herd immunity happens when most of the animals in a group are immune to an infection. If most animals are immune they cannot get the disease. If they do not get the disease, they cannot give it to other animals. So even one animal who is not immune is safer. If none of the other animals in a herd get the infection, they cannot give the infection to the one who is non immune.
This is important in people too. If 95% of people in a place are immune from a disease, the other 5% are safer. There will just not be as much of that disease around to get.
The people who are in the 5% are there for many reasons. Some got the vaccine but did not react to it. Their immune system did not learn how to fight it well. Some of them are too sick to get the vaccine. It can be children who are too sick with other diseases to get vaccines. It can be a pregnant woman who cannot get the vaccine because it could hurt her baby. It can be a person with cancer who does not have a strong immune system. It can be an older person who has a weak immune system.
So if everyone in a place gets vaccinated, it protects these people too. If they are not protected by herd immunity, they can get more sick from an infection. They get the infection more easily and they get sicker from it. So it is important that people who are healthy get their vaccinations. It protects the healthy people. But it also is important to protect other people who are old, weak, or sick.
[change] Types of vaccines
There are different types of vaccines:
- Inactivated vaccines contain particles (usually viruses). These have been grown for the purpose. They have been killed, using formaldehyde or by other means. But the virus still looks intact; the immune system can develop antigens against it.
- Attenuated vaccines contain live viruses, that have been weakened. They will reproduce, but very slowly. Such vaccines cannot be used on patients with a weakened immune system.
- Subunit vaccines show antigens to the immune system, without introducing virus material.
[change] Safety of vaccination
Some people argue against vaccination. They believe giving people vaccination causes more sickness than it stops. Today in modern countries, most people are vaccinated. Because most people are vaccinated much fewer people get sick from the infections that vaccines stop. So most people do not think about the risk of getting these infections. Many young doctors have not even seen some of these diseases!
Vaccines also can make people very sick. Almost all people who get a vaccination do not get sick from it. Some people get a little sick. They may get fever or feel sick. This gets better in a few days. A very very small number of people can get very sick. So people see that vaccines can make people sick. But they do not see how sick more people would be if we did not vaccinate people. So they only think about the risks vaccines cause. They do not think as much about the risks of not giving vaccinations.
Some people chose not to get vaccinations because of the small risks. Parents may not give their children vaccines. These people also depend on herd immunity. If most children do not get mumps children who do not get the mumps vaccine are also safe. But if enough children do not get the mumps vaccine, or if the vaccine does not work as well as expected, mumps comes back, afflicting older people for whom the disease is more severe. That would be called an epidemiological shift. Then all people who are not immune may get sick. These might be healthy people who chose not to get the vaccine. They might get sick, but will usually get well. Sick people who depend on herd immunity will also get sick. Some may get very sick and even die.
All big medical organizations say that vaccines are safe. They say vaccines stop much more sickness than they make. The World Health Organization, the American Medical Association, the American Academy of Pediatrics, and the United States Centers for Disease Control all support vaccination.
[change] Other websites
These may be unsimple:
- World Health Organization about vaccines
- Sabin Vaccine Institute
- Jenner Institute for Vaccine Research
- Walter Reed National Vaccine Healthcare Centers Network (US)
- American Academy of Pediatrics Vaccine Information
