How vaccines work. Prevention of diseases

Your Immune System (lymphatic system) It is always better to prevent a disease than to treat it after it occurs. Immunity is the body’s way of preventing/fighting disease. The immune system recognizes molecules from germs to proteins that enter the body as "foreign invaders” (called antigens). Produces proteins called antibodies to help fight them.

How your Immune system works, The first time a child is infected with a specific antigen (say measles virus), the immune system produces proteins called antibodies designed to identify it. This takes time... usually the immune system can’t work fast enough to prevent the antigen from causing disease (lysis), so the child still gets sick. However, the immune system “remembers” that antigen by producing memory cells. If it ever enters the body again, even after many years, the immune system can produce antibodies fast enough to keep it from causing disease a second time (lysis). This protection is called immunity. Vaccines artificially program this system w/o exposure to the natural version of viruses / bacteria

Types of vaccine 1) Live-attenuated vaccines: Active, but very weak Vaccines made when the virus is weakened to such a level that they reproduce only about 20 times in the body. By comparison, natural viruses reproduce thousands of times. "Live-attenuated vaccines can cause very mild illness in a small proportion of people," says John Bradley, M.D., member of the committee on infectious diseases of the American Academy of Pediatrics (AAP). "However, these side effects are usually very mild and limited to a low-grade fever or runny nose." Dr. Bradley also notes that about 5 to 10 percent of children who receive the varicella (chickenpox) vaccine develop a few pox spots, but it's nothing compared to the full-blown illness.

Types of Live-attenuated vaccines Example/recommended: Measles, mumps, rubella (MMR combined vaccine) Varicella (chickenpox) Influenza (nasal spray) Rotavirus (Stomach Flu) Others: Zoster (shingles), Yellow fever

2) Inactivated vaccines: The bacteria/virus is completely killed using a chemical Inactive / dead pathogens used The strength of these vaccines tend to wear off over time, resulting in less long-lasting immunity. So, multiple doses of inactivated vaccines are usually necessary to provide the best protection. Examples: hepatitis A, hepatitis B, poliovirus, haemophilus influenzae type b (Hib), meningococcal, pneumococcal and the injected form of influenza.

3) Subunit Vaccines Only the antigens/part of the capsid that best stimulate the immune system. Subunit vaccines can contain anywhere from 1 to 20 or more antigens/capsids. They can grow the microbe in the laboratory and then use chemicals to break it apart and gather the important antigens/capsids. A recombinant subunit vaccine has been made for the hepatitis B virus. Scientists inserted hepatitis B genes that code for important antigens into common baker’s yeast. The yeast then produced the antigens, which the scientists collected and purified for use in the vaccine. Research is continuing on a recombinant subunit vaccine against hepatitis C virus. Examples Hepatitis B Influenza (injection) Haemophilus influenza type b (Hib) Pertussis (DTaP combined immunization) HPV

4) Toxoid Vaccines For bacteria that secrete toxins, or harmful chemicals as main cause of illness. Inactivate toxins by treating them with formalin, a solution of formaldehyde and sterilized water. Such “detoxified” toxins, called toxoids. Immune system receives a vaccine containing a harmless toxoid, it learns how to fight off the natural toxin. The immune system produces antibodies that lock onto and block the toxin. Example: Diphtheria, tetanus (part of DTaP combined immunization)

TED Talk on vaccines