Types of Vaccines
There are several different types of vaccines. The three main types are described below.
Live attenuated vaccines
Live vaccines are made from a weakened (attenuated) version of the pathogen (virus or bacteria) that causes the disease. When a person receives a live vaccine, the virus or bacteria in the vaccine multiplies (grows) in the body and stimulates an immune response almost identical to that produced by natural infection. Because it is weakened, the vaccine germ cannot multiply enough to cause disease in people with healthy immune systems. However, live vaccines are not given to people with very weak immune systems as they may develop the disease the vaccine is meant to protect against.
One dose of a live vaccine usually produces immunity and long-lasting protection due to the strong immune response. But because not all individuals respond to the first dose, a second dose is usually recommended. The measles, mumps, rubella (MMR) and chickenpox (varicella) vaccines are examples of live attenuated vaccines.
Inactivated vaccines are made from a killed version of the pathogen (virus or bacteria) that causes the disease. Since the pathogen used to make these vaccines is killed, it is not able to multiply in the vaccinated person and this leads to a weaker immune response compared to live vaccines. Due to the weaker immune response, inactivated vaccines almost always require multiple doses. These vaccines are safe even for those with weakened immune systems, because the killed germ cannot cause disease. The polio, hepatitis A and influenza (flu) vaccines are examples of inactivated vaccines.
Subunit vaccines are made using only parts of the disease-causing pathogen, such as a protein, inactivated toxin or sugar. Some types of subunit vaccines are made using genetic engineering. Like inactivated vaccines, subunit vaccines do not contain live components of the pathogen and are safe even for those with weakened immune systems, but often require multiple doses. The diphtheria, tetanus, pertussis, hepatitis B, pneumococcal, meningococcal and human papillomavirus vaccines are all examples of subunit vaccines.
Watch the video to learn more about the different types of vaccines. The video also includes a quick review of how the immune system and vaccines work. After watching the video by Kelwalin Dhanasarnsombut, test your knowledge with the quiz and earn vaccines!