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How vaccines work ? Are they beneficial ? How!! Science about vaccination

How vaccines work ? Are they beneficial ? How!! Science about vaccination 


Vaccines prevent diseases that can be dangerous or even fatal. Vaccines cooperate with the body's natural defense system to safely develop immunity to disease, greatly reducing the risk of infection. This fact sheet explains how the body fights infections and how vaccines protect humans by generating immunity.Immune System-The body's defense against infections

To understand how vaccines work, first look at how the body fights disease. When bacteria such as bacteria or viruses invade the body, they will attack and multiply. This invasion is called infection, and infection is the cause of the disease. The immune system uses multiple tools to fight infection. The blood contains red blood cells used to deliver oxygen to tissues and organs, and white blood cells or immune cells used to fight infections. These white blood cells are mainly composed of B lymphocytes, T lymphocytes and macrophages:

  • Macrophages are white blood cells that engulf and digest bacteria, as well as dead or dying cells. Macrophages leave a part of the invading bacteria called antigens. It is dangerous for the human body to recognize antigens and stimulate the body to attack them.
  • Antibodies attack antigens left by macrophages. Antibodies are produced by defensive white blood cells called B lymphocytes .
  • T lymphocytes are another type of defensive white blood cells. They attack cells in the infected body.

When the human body is exposed to bacteria for the first time, it may take several days to manufacture and use all the required sterilization tools to overcome the infection. After infection, the immune system remembers how to protect the body from this disease.
The body retains some T lymphocytes, called memory cells, and if the body encounters the same bacteria again, it will act quickly. When familiar antigens are found, B lymphocytes produce antibodies that attack them.

How vaccines work

Vaccines help to develop immunity by mimicking infections . However, this type of infection does not cause disease, but it does cause the immune system to produce T lymphocytes and antibodies. Sometimes, after vaccination, this imitation infection can cause mild symptoms such as fever. These mild symptoms are normal and should be performed when the body establishes immunity.
Once the imitation infection disappears, the body will leave some "memory" T lymphocytes, as well as b lymphocytes, they will remember how to fight this disease in the future. However, after vaccination, it usually takes a few weeks for the human body to produce T and B lymphocytes. Therefore, because the vaccine does not have enough time to provide protection, people who are infected with a certain disease before or after vaccination may develop symptoms and develop a certain disease.

Types of vaccines

Scientists have used many methods to design vaccines. These methods are based on information about the bacteria (virus or bacteria) that the vaccine will prevent, such as how it infects cells and how the immune system responds to it. Practical considerations, such as areas in the world where vaccines are used, are also important because the strains and environmental conditions of a virus, such as temperature and exposure risk, may be different around the world. The available vaccination protocols may also vary geographically. Today, babies and young children are usually vaccinated in five main types of vaccines:

  • Live attenuated vaccines fight the virus . These vaccines contain a live virus that has been weakened, so it will not cause serious diseases for people with healthy immune systems. Because live attenuated vaccines are the closest to naturally infected vaccines, they are good teachers of the immune system. Examples of live attenuated vaccines include measles, mumps and rubella vaccines (MMR) and varicella (chickenpox) vaccines. Although these vaccines are very effective, not everyone can accept them. Children with weakened immune systems-such as children undergoing chemotherapy-cannot receive live vaccines.
  • Inactivated vaccines can also fight viruses . These vaccines are made by inactivating or killing viruses during the preparation of vaccines. An inactivated polio vaccine is an example of such a vaccine. Inactivated vaccines produce an immune response in a different way than live attenuated vaccines. Usually, multiple injections are required to establish and / or maintain immunity.
  • Toxoid vaccines prevent diseases caused by bacteria that produce toxins (poisons) within the body. In the process of making these vaccines, the toxins are weakened, so they will not cause disease. The weakened toxin is called toxoid. When the immune system is vaccinated with a toxoid, it will learn how to fight against natural toxins. The DTaP vaccine contains diphtheria and tetanus toxoid.
  • Subunit vaccines include only part of the virus or bacteria or subunits, not the entire bacteria. Because these vaccines contain only the necessary antigens and not all the molecules that make up bacteria, side effects are less common. The pertussis (pertussis) component of the DTaP vaccine is an example of a subunit vaccine.
  • Combined vaccines can fight different types of bacteria . These bacteria have antigens, and the outer layer is carbohydrate, called polysaccharide. This type of coating masks the antigen, making it difficult for young children's immature immune system to recognize and respond to it. Conjugate vaccines are effective against these types of bacteria because they connect (or bind) polysaccharides to antigens that respond well to the immune system. This connection helps the immature immune system react to the coating and produce an immune response. An example of such a vaccine is the Haemophilus influenzae type b (Hib) vaccine.

Vaccines require more than one dose
of babies who are vaccinated for the first time--even adolescents or adults--for more than four reasons, more than one dose of vaccine may be needed:

  • For some vaccines (mainly inactivated vaccines), the first injection cannot provide as much immunity as possible. Therefore, more than one dose is needed to build a more complete immunity. A vaccine against the Hib bacterium that causes meningitis is a good example.
  • In other cases, such as the DTaP vaccine that protects against diphtheria, tetanus, and whooping cough, as part of the immunization of infants, the children's initial four-shot vaccine helps them establish immunity. However, after a while, this immunity began to disappear. At this time, "enhancers" are needed to restore immune levels. DTaP requires the use of this synergist between the ages of 4 and 6. At the age of 11 or 12, another booster for these diseases is needed. This enhancer for older children-as well as adolescents and adults-is called Tdap.
  • For some vaccines (mainly live vaccines), research shows that everyone needs more than one dose of vaccine to produce the best immune response. For example, after a dose of MMR vaccination, some people may not produce enough antibodies to fight infection. The second dose helps ensure that almost everyone is protected.
  • Finally, for flu vaccines, adults and children (over 6 months) need to be injected once a year. Children from 6 months to 8 years of age who have never been vaccinated against influenza or who have been vaccinated only once in the past few years require two doses in the first year of influenza vaccination for optimal protection. Then, flu vaccines need to be given every year, because the virus that causes the disease may be different every year. Every year, influenza vaccines are designed to prevent specific viruses that experts predict will spread.

Bottom line
Some people think that the naturally obtained immunity is much better than the immunity provided by the vaccine. However, natural infections can cause serious complications and be fatal. This is true even for diseases that most people consider to be milder, such as chickenpox. It is impossible to predict who will be seriously infected that may lead to hospitalization.
As with any medicine, vaccines can cause side effects. The most common side effects are mild. However, many vaccine-preventable disease symptoms can be severe or even fatal. Although many of these diseases are rare in some countries, they do spread throughout the world and may be brought to the United States, putting unvaccinated children at risk. Even with advances in health care, the diseases that vaccines prevent can still be very serious-vaccination is the best way to prevent these diseases.

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