Types of Vaccines
A vaccine is a biological preparation that provides immune protection against infections. Vaccines contain antigens, which are substances that induce an immune response. When a person is vaccinated, they are exposed to the antigens in the vaccine, which causes their immune system to produce antibodies. The antibodies help protect the person from infection by the disease that the vaccine is meant to prevent.
There are four types of vaccines:
- live attenuated
Live Attenuated Vaccines
Live attenuated vaccines (LAV) use a weakened form of the virus or bacteria to provoke an immune response. LAVs are used to vaccinate against many diseases, such as measles, mumps, rubella, and influenza. How does a LAV work?
When a person is vaccinated with a LAV, they are injected with the weakened form of the virus or bacterium. This weakened form can replicate inside the body but isn’t strong enough to cause disease. As it replicates, it creates an immune response in the body and helps the person develop immunity to the disease. The viruses or bacteria in LAVs are often attenuated (weakened).
Inactivated vaccines use dead viruses or bacteria to stimulate immunity. These vaccines use viruses, bacteria, or other organisms that have been grown in a laboratory and then killed before they are used to immunize someone. Inactivated vaccines are sometimes called “killed” or “whole-cell” vaccines.
The process of making an inactivated vaccine usually starts with selecting the viruses, bacteria, or other organisms to be used in the vaccine. The next step is to grow the selected organism in large quantities in the laboratory. After the organism has been grown, it is exposed to a special kind of heat or chemicals that kills it. Once it is killed, it can’t cause infection anymore. When these weakened viruses or dead bacterial particles enter our body, our immune system recognizes them as ‘foreign invaders’.
Toxoid vaccines use toxins produced by bacteria to trigger immunity. This vaccine contains inactivated toxins. Toxins are poisonous substances produced by bacteria or other organisms. Inactivating the toxin makes it safe to use in a vaccine. When you receive a toxoid vaccine, your body produces immunity (protection) against the disease caused by bacteria or other organisms.
Toxoid vaccines are used to protect against diphtheria and tetanus. Diphtheria and tetanus are serious diseases caused by bacterial toxins. The diphtheria toxoid vaccine is usually given as part of the DTaP vaccination (diphtheria, tetanus, and pertussis). The DTaP vaccination is given to children under seven years of age.
Subunit vaccines use only pieces of the virus or bacteria to generate immunity. A subunit vaccine is made from only a part of the virus or bacterium. For example, some flu vaccines are made from just one protein from the flu virus. These vaccines can be made more quickly. They also might be easier to make if there is a shortage of the virus or bacterium.
Subunit vaccines usually work by causing the body to produce immunity against the part of the virus or bacterium that is used to make the vaccine. This type of immunity is called cellular immunity because it involves cells in your body, such as T cells and B cells. Cellular immunity protects you from disease by attacking viruses or bacteria inside your body.
When you get a subunit vaccine, your body recognizes the antigen as foreign and produces antibodies. If you ever encounter a real virus or bacterium, your body will already have some antibodies ready to fight.