How Does a Vaccine Work Within the Body?
Vaccines offer a possible solution to COVID19. To understand how vaccines work, it is necessary to first look at how the body naturally fights illness. Humans live in a world heavily populated with disease causing microbes and toxins. The immune system has evolved to defend the body against these foreign or dangerous invaders. To defend the body against infection, the immune system must be able to distinguish between what naturally belongs in the body and what does not.
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Antigens are any substances that the immune system can recognize as foreign and that can stimulate an immune response. The immune response is activated if the body encounters an antigen that is perceived as dangerous. When germs invade the body, they attack the body and multiply. This invasion is what causes illness. The body’s immune system uses several tools to fight these infections. These mechanisms are the immune response and they include: 1) recognizing a potentially harmful foreign antigen, 2) activating and mobilizing forces to defend against it, 3) attacking and destroying the invader, and 4) stationing sentinels, called memory cells, that remain ready for action. There are several components of the immune system involved in this immune response. These include white blood cells, such as B-lymphocytes, T-lymphocytes, and macrophages, as well as antibodies.
Antibodies are proteins that are produced by the B-lymphocytes that tightly bind to the antigen of an invader, tagging it for attack. Each antibody is specific to a given antigen. B-lymphocytes are responsible for recognizing the invading antigens and producing antibodies that attach to the invading pathogens identifying them for the T-lymphocytes. The T-lymphocytes are killer (cytotoxic) cells that attach to invading cells to attack and destroy them. Macrophages are large cells that ingest and eliminate dead and dying pathogens after they have been destroyed by the cytotoxic cells. Even after the invaders have been eliminated, the body keeps a few T-lymphocytes and B-lymphocytes, as memory cells, that go into action quickly if the same invader is encountered again. This is called acquired immunity.
The immune system is an efficient system protecting us from a host of illnesses we have encountered and overcome in the past. Unfortunately, the first time the body faces an invasion, it can take several days to ramp up this antibody response. For lethal antigens like Ebola or influenza, a few days can be too long. The infection can spread and kill the person before the immune system can fight back.
Vaccines offer a solution to this problem. They help to develop immunity without the body having to first survive an illness. These vaccines are made from weakened or killed germs that are introduced into the body before the actual germ has been encountered. These crippled germs help to develop immunity by imitating an infection and stimulating the body to produce antibodies and memory cells. These cells stay in the body and remember how to fight the infection in the future. If the body is invaded by these germs, the immune system will spring into action to destroy the invaders before the disease can become established.
The development of vaccines is a long and complex process, often taking ten to fifteen years. This process includes the identification of the antigen from a deactivated portion of the virus, the production of the vaccine, the extensive testing of the vaccine through a series of trials exposing larger and larger numbers or subject to the trial vaccine after its safety has been verified, and the evaluation of data gathered during the trials to determine the effectiveness of the vaccine. In the case of COVID-19, governments around the world have streamlined the process by removing many of the traditional regulations. Many expect that this will cut the process in this case to 12 to 18 months. On March 30th Johnson and Johnson announced the selection of a lead COVID-19 vaccine candidate. The company expects to start human trials by September, at the latest, and anticipates the first batches of a vaccine could be available for in early 2021.
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