There are different types of vaccines that are designed to trigger the immune system to protect against infections caused by bacteria or viruses. This protection usually involves stimulating the body to produce antibodies against infection and disease.
A weakened or attenuated form of the bacteria or virus is used to make these vaccines. This type of vaccine causes strong and long-lasting immune responses against infection and disease that are similar to what happens after natural infection. Booster doses may be needed over time to maintain the level of protection.
Examples of live-attenuated vaccines include those against measles, mumps, and rubella.
A killed version of the bacteria or virus is used in this vaccine. This type of vaccine usually does not provide the same level of protection as live-attenuated vaccines, and may require booster doses to maintain ongoing immunity against infection and disease.
Examples of inactivated vaccines include those against hepatitis A and influenza.
Specific pieces of the bacteria or virus are used in these vaccines, such as a protein. They lead to strong immune responses against infection and disease. Booster doses may be needed over time to maintain the level of protection.
Examples of these types of vaccines include those against hepatitis B and human papillomavirus.
Toxins made by certain bacteria are used in these vaccines. The immune system responds to the toxin to protect people from disease. Booster doses are needed over time to maintain the level of protection.
Examples of these types of vaccines include those against tetanus and diphtheria.
For this vaccine type, a virus is used as a “vector” to trigger an immune response that prevents infection and disease caused by a different virus. Adenovirus is often the viral vector used for this purpose. This vaccine type can mimic natural infection and therefore results in strong immune responses. Because some people may previously have been exposed to the virus being used as a vector, they may not respond as well to these vaccines, which can make them less effective.
Examples of these types of vaccines include those against Ebola.
Genetic material of the virus, either RNA or DNA, is used in this vaccine type. In the case of vaccines against COVID-19, the messenger RNA (“mRNA”) in the vaccines causes the immune system to produce a form of the COVID-19 protein that stimulates the production of antibodies which protect against infection and disease.
The COVID-19 vaccines using RNA are the first in this category to be authorized for human use.