Molly Macek
MCB2004

BCG Vaccine
General Introduction: A vaccine is a biological matter that is used to protect people from a particular disease. Vaccines provide active acquired immunity, which is that they provide protection by introducing a substance that contains the agent. The diseases that vaccines protect people from cause very serious illnesses and in some cases can cause death. When foreign substances, such as viruses or bacteria, invade our bodies an infection occurs which causes the illness. Vaccines work with our bodies natural defense system to gain immunity to a particular disease.
A vaccine gives our bodies immunity by mimicking an infection, but in most cases does not cause the illness. Although there should be no illness, vaccines cause our bodies to respond as it would if were real infection so that in the future our bodies can recognize this invasion and we can be protected from it. When a large number of people in a population are immune to a particular infection ; it is called herd immunity. Herd immunity is important because it helps slow down the spreading of diseases. If more people in a community are immune it will decrease the amount of interactions of those that are not immune with an infectious disease.
Weakening the virus or bacteria so that the individual can be provided with the immune response develops vaccines. One general strategy in developing viruses is weakening the virus so that they multiply ineffectively once inside the body. One limitation of this method is that these vaccines cannot be given to people with weakened immune systems such as people with AIDS. Another way to make a vaccine is by inactivating the virus by completely killing it. When this happens it cannot cause the disease, but our bodies still recognize it so that we can protect from it. One constraint of these types of vaccines is that it can require multiple doses to work effectively. Before these vaccines can be developed, scientists must spend a lot of time studying, researching, and isolating the virus or bacteria that is causing these diseases. They have to make sure that the vaccine is safe and also that it will do its job.
There are some misconceptions about vaccines. One in particular according to the History of Vaccines is that “ more vaccinated than unvaccinated get sick.” in some cases vaccinated people will still get stick because they are not 100% effective, but this is very rare. Also there are usually more vaccinated people than unvaccinated so it may seem like more vaccinated people get sick but that is only because so many more people are vaccinated.
The Vaccine Against Tuberculosis:
Bacillus Calmette-Guerin, formally known as Vaccin Billie de Calmette et Guerin and commonly known as BCG is a vaccine used to protect people against tuberculosis (TB). Hoping that a bovine BCG vaccine could help against TB discovered this vaccine. The tested the vaccine in cattle, pigs and other animals before a human trial on an infant. Shortly after the vaccine was proved to be safe and they started to manufacture it. BCG is given as a single skin injection.
BCG is prepared by using a live strain of Myobacterium bovis that was discovered by Calmette and Guerin. This particular strain does not adapt well in human blood when introduced in a human and does not cause the disease. Before the BCG vaccine is delivered a tuberculin skin test should always be done. If the test is positive a BCG is not recommended.
The rate of efficacy of BCG vaccines has varied over the years, and has been affected by the methods in which the vaccine was administered. In a recent study conducted in the United States showed that this vaccine had an 86% protective effect (CDC MMWR).
The Disease:
Tuberculosis (TB) is a result of the invasion of the bacteria Myobacterium tuberculosis. It usually attacks the lungs, but in some cases it will attack other parts of the body such as the kidneys or spleen. Tuberculosis is spread through the air when