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Immunization, Vaccines & their types. Dr. Asif Rehman. Vaccines. Difference between vaccination and immunization?. Definitions. Immunity : Protection from an infectious disease. If you are immune to a disease, you can be exposed to it without becoming infected .
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Immunization,Vaccines & theirtypes Dr. Asif Rehman
Vaccines Difference between vaccination and immunization?
Definitions • Immunity: Protection from an infectious disease. If you are immune to a disease, you can be exposed to it without becoming infected. • Vaccination: The act of introducing a vaccine into the body to produce immunity to a specific disease. • Immunization: A process by which a person becomes protected against a disease through vaccination.
Immunity • Immunity to a disease is achieved through the presence of antibodies to that disease in a person’s system. Antibodies are proteins produced by the body to neutralize or destroy toxins or disease-carrying organisms. • Antibodies are disease-specific. For example, measles antibody will protect a person who is exposed to measles disease, but will have no effect if he or she is exposed to mumps.
Why it is important • From the moment babies are born, they are exposed to numerous bacteria and viruses on a daily basis. • Eating food introduces new bacteria into the body; numerous bacteria live in the mouth and nose; and an infant places his or her hands or other objects in his or her mouth hundreds of times every hour, exposing the immune system to still more germs.
Types of Immunity 2 types of immunities • Active immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Exposure to the disease organism can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease organism through vaccination (vaccine-induced immunity). Either way, if an immune person comes into contact with that disease in the future, their immune system will recognize it and immediately produce the antibodies needed to fight it. • Active immunity is long-lasting, and sometimes life-long.
Types of immunity • Passive immunity is provided when a person is given antibodies to a disease rather than producing them through his or her own immune system. • A newborn baby acquires passive immunity from its mother through the placenta. A person can also get passive immunity through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed. This is the major advantage to passive immunity; protection is immediate, whereas active immunity takes time (usually several weeks) to develop. • However, passive immunity lasts only for a few weeks or months. Only active immunity is long-lasting.
Vaccine • A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease. Vaccines are usually administered through needle injections, but can also be administered by mouth or sprayed into the nose.
Types of Vaccines • Live, attenuated vaccines • Inactivated vaccines • Toxoid vaccines • Subunit vaccines • Conjugate vaccines
Live, attenuated vaccines • These vaccines contain a version of the living virus or bacteria that has been weakened so that it does not cause serious disease in people with healthy immune systems. Because live, attenuated vaccines are the closest thing to a natural infection. • Examples of live, attenuated vaccines include measles, mumps, and rubella vaccine (MMR) and varicella (chickenpox) vaccine. Even though they are very effective, not everyone can receive these vaccines. Children with weakened immune systems—e.g, those who are undergoing chemotherapy—cannot get live vaccines.
Inactivated vaccines • These vaccines are made by inactivating, or killing, the germ during the process of making the vaccine. • The inactivated polio vaccine (IPV) is an example of this type of vaccine. • Inactivated vaccines produce immune responses in different ways than live, attenuated vaccines. Often, multiple doses are necessary to build up and/or maintain immunity
Toxoid vaccines • Prevent diseases caused by bacteria that produce toxins (poisons) in the body. In the process of making these vaccines, the toxins are weakened so they cannot cause illness. • Weakened toxins are called toxoids. When the immune system receives a vaccine containing a toxoid, it learns how to fight off the natural toxin. • The DPTvaccine contains diphtheria and tetanus toxoids.
Subunit vaccines • Include only parts of the virus or bacteria, or subunits, instead of the entire germ. Because these vaccines contain only the essential antigens and not all the other molecules that make up the germ, side effects are less common. • The pertussis (whooping cough) component of the DPT vaccine is an example of a subunit vaccine.
Conjugate vaccines • Fight a different type of bacteria. These bacteria have antigens with an outer coating of sugar-like substances called polysaccharides. This type of coating disguises the antigen, making it hard for a young child’s immature immune system to recognize it and respond to it. • Conjugate vaccines are effective for these types of bacteria because they connect (or conjugate) the polysaccharides to antigens that the immune system responds to very well. This linkage helps the immature immune system react to the coating and develop an immune response. • An example of this type of vaccine is the Haemophilus influenzaetype B (Hib) vaccine.
Early Vaccination • Children are exposed to thousands of germs and other antigens in the environment from the time they are born. When a child is born, his/her immune system is ready to respond to the many antigens in the environment and the selected antigens in vaccines.
Early Vaccination • Children are given vaccines at a young age because this is when they are at highest risk of getting sick. • Newborn babies are immune to some diseases because they have antibodies they get from their mothers, usually before they are born. However, this immunity lasts a few months. • Most babies do not get protective antibodies against diphtheria, whooping cough, polio, tetanus, hepatitis B, or Hib from their mothers. This is why it’s important to vaccinate a child before she or he is exposed to a disease.
Ingredient of vaccine • Suspending fluid (e.g. sterile water, saline, or fluids containing protein); • Preservatives and stabilizers to help the vaccine remain unchanged (e.g. albumin, phenols, and glycine) • Aluminum gels or salts of aluminum which are added as adjuvants to help the vaccine stimulate a better response. Adjuvants help promote an earlier, more potent response, and more persistent immune response to the vaccine. • Antibiotics which are added to some vaccines to prevent the growth of germs (bacteria) during production and storage of the vaccine.
Ingredient of vaccine • Formaldehyde is used to inactivate bacterial products for toxoid vaccines, (these are vaccines that use an inactive bacterial toxin to produce immunity.) It is also used to kill unwanted viruses and bacteria that might contaminate the vaccine during production. Most formaldehyde is removed from the vaccine before it is packaged. • Monosodium glutamate (MSG) and 2-phenoxy-ethanol which are used as stabilizers in a few vaccines to help the vaccine remain unchanged when the vaccine is exposed to heat, light, acidity, or humidity. • Thimerosal is a mercury-containing preservative that is added to vials of vaccine that contain more than one dose to prevent contamination and growth of potentially harmful bacteria.
Combination vaccines • Many vaccines are recommended early in life to protect young children from dangerous infectious diseases. In order to reduce the number of shots a child receives in a doctor’s visit, some vaccines are offered as combination vaccines. A combination vaccine is two or more different vaccines that have been combined into a single shot. E.g Pentavalent. • Giving a child several vaccines during the same visit offers two advantages. 1) Avoids several shots. 2) saves time and money
Vaccines not recommended during pregnancy • HPV • MMR • Some kinds of flu vaccines • Varicella (chicken pox)
Keep immunizing until disease is eliminated. • Unless we can eliminate the disease, it is important to keep immunizing. Even if there are only a few cases of disease today, if we take away the protection given by vaccination, more and more people will become infected and will spread disease to others. Soon we will undo the progress we have made over the years
Life cycle of immunization program • When there is no vaccine for a disease, the number of people getting the disease is usually high. People worry about the disease and its complications. • After an immunization program for a disease begins, the number of people being vaccinated usually rises quickly. • At the same time, there will be some adverse reactions associated with the vaccine — almost always very few and very mild compared with illness and complications associated with the disease. • As the number of people being vaccinated rises, the number of cases of disease drops. Eventually, the number of people getting the disease may approach, or even fall below, the small number of people having reactions from the vaccine.
Life cycle of immunization program • At this point, most people may never have experienced the disease. They might start to worry less about the disease and more about possible side-effects from the vaccine. They might start to question whether the vaccine is necessary or safe, and some of them will stop getting immunized. • If enough people stop getting immunized, disease numbers will start to rise again, and there will be disease outbreaks. • People are reminded of how bad the disease can be, and turn back to immunization to avoid it. Vaccination numbers rise once more and disease numbers fall.
Difference between IPV and OPV • IPV is Inactivated (killed) virus vaccine while Oral Polio Vaccine is a live attenuated (harmless) vaccine • IPV is more effective and has less risk of side effects as virus in vaccine is already killed. It is less heat sensitive. Weak point is that it does not provide local gut immunity as OPV. • OPV is to be given by mouth. Less immunogenic and therefore more doses are required(at least 6). This needs efficient thermal protection. Since this vaccine is given by mouth and proliferates in intestine, it provides excellent local protection. Moreover, when excreted in stool, it makes herd immunity by feco-oral route. • Both these vaccines have distinct advantages. IPV is safe and more effective but costly and in short supply.
