by Dr. E V Kumar
Vaccines are made in several ways. However, all vaccines have the same general goal: weaken the virus or bacteria in a way that allows the recipient to develop an immune response without developing any symptoms of infection. Vaccines are made using the same components that are found in the natural virus or bacteria.
Weaken the virus
Using this strategy, viruses are weakened so that they reproduce themselves very poorly once inside the body. The measles, mumps, German measles (rubella), rotavirus, intranasal influenza and chickenpox (varicella) vaccines are made this way. Whereas natural viruses reproduce themselves thousands of times, vaccine viruses usually reproduce themselves fewer than 20 times. Because vaccine viruses don’t reproduce themselves very much, they don’t cause disease, but vaccine viruses replicate well enough to induce “memory cells” that protect against infection in the future.The advantage of live, “weakened” vaccines is that one or two doses provide immunity that is life-long.
Inactivate the virus
Using this strategy, viruses are completely inactivated (or killed) with a chemical. By killing the virus, it cannot possibly reproduce itself or cause disease. The inactivated polio, hepatitis A, influenza (shot), and rabies vaccines are made this way. Because the virus is still “seen” by the body, cells of the immune system that protect against disease are generate. However, the limitation of this approach is that it typically requires several doses to achieve immunity.
Use part of the virus
Using this strategy, just one part of the virus is removed and used as a vaccine. The hepatitis B and HPV vaccines are made this way. The vaccine is composed of a protein that resides on the surface of the virus. This strategy can be used when an immune response to one part of the virus (or bacteria) is responsible for protection against disease
Use part of the bacteria
Some bacteria cause disease by making a harmful protein called a toxin. Several vaccines are made by taking toxins and inactivating them with a chemical (the toxin, once inactivated, is called a toxoid). By inactivating the toxin, it no longer causes harm. The diphtheria, tetanus and pertussis vaccines are made this way. Just like for inactivated viral vaccines, bacterial vaccines require several doses to induce adequate immunity.
