Types of Vaccines
There are several types of vaccines, each well-suited to prevent different diseases. When administered, vaccines trigger your body's defenses which create antibodies to fight the bacteria or virus.
The small amount of virus or bacteria that vaccines contain is much weaker than what your child may encounter naturally, and are designed to prepare the immune system to defend against the disease.
The scientific community chooses what type of vaccine to develop based upon the characteristics of the infecting agent (bacteria, virus or toxin), and then works to make the safest vaccine possible.
Over time, the type of vaccine may change for a given disease. For example, protection from polio infection in the United States was once achieved by getting the oral polio vaccine which is a live attenuated vaccine (see below). The drawback to that vaccine was that some people could get polio from the vaccine. But once polio was declared eradicated in the United States, we switched to the Inactivated Polio Vaccine which cannot cause the recipient of the vaccine to get polio.
Here are the main types of vaccines:
- Live Attenuated Vaccines: These vaccines are made up of living virus or bacteria that have been weakened (attenuated) by scientists. These vaccines are very effective, but in rare cases (such as in people with compromised immune systems), can cause infection.
- Inactivated Vaccines: More stable than live vaccines, these vaccines contain disease microbes that have been killed with chemicals. Inactivated vaccines tend to stimulate a weaker immune response than live vaccines, and may require booster shots to maintain immunity.
- Toxoid vaccines: When the cause of illness is a toxin that the virus or bacteria emits, scientists may be able to formulate a vaccine from just the deactivated toxin, rather than the whole bacteria. When the vaccine is administered, the immune system learns to fight off the toxin.
- Conjugate Vaccines: Some bacteria have special coatings that hide them from the immune system. Conjugate vaccines link these coatings to an organism that an immature immune system can recognize, so it can respond and produce immunity.
- Subunit Vaccines: These vaccines are made with only the parts of the microbe that stimulate the immune system. Subunit vaccines can be made by taking apart the actual microbe, or they can be made in the laboratory using genetic engineering techniques. Since these vaccines contain only parts of the microbe rather than the whole microbe, the chance of temporary reactions is even lower than with other kinds of vaccines.