Vaccines are a critical tool in controlling and preventing infectious diseases. They work by training and preparing the body's natural defenses -- the immune system -- to recognize and fight off the viruses and bacteria they target. If the body is exposed to those disease-causing germs later, the body is immediately ready to destroy them, preventing illness.
There are several
types of vaccines. Each type is designed to teach your immune system how to fight off certain kinds of germs— and the serious diseases they cause.
Live, attenuated vaccines fight viruses and bacteria. These vaccines contain a version of the living virus or bacteria that has been weakened so it does not cause serious disease in people with healthy immune systems.
Inactivated vaccines also fight viruses and bacteria. These vaccines are made from the virus or bacteria that has been killed or parts of the virus or bacteria.
Subunit, recombinant, polysaccharide, and conjugate vaccines are made from pieces of the virus or bacteria. Because these vaccines use only specific pieces of the germ, they give a very strong immune response that’s targeted to key parts of the germ.
Toxoid vaccines are used against bacteria that produce toxins (poisons). The toxins are weakened so they cannot cause illness and are used to create the vaccine. When the immune system receives a vaccine containing a harmless toxoid, it learns how to fight off the natural toxin.
mRNA vaccines contain material from the virus that causes COVID-19 that gives our cells instructions for how to make a harmless protein that is unique to the virus. After our cells make copies of the protein, they destroy the genetic material from the vaccine.
Vaccines work by mimicking the infectious bacteria or viruses that cause disease. Vaccination stimulates the body's immune system to build up defenses against the infectious bacteria or viruses (or parts of them) but does not cause the disease. The components of the vaccine that stimulate the immune system are called antigens.
Vaccines are important for reasons beyond just individual protection. When enough people are vaccinated, it helps to establish what is called herd immunity or community immunity. This means that even those who cannot get vaccinated for medical reasons get some protection because the spread of contagious disease is limited.
Yes, vaccines are
safe. The benefits of vaccination greatly outweigh the risk, and many more illnesses and deaths would occur without vaccines. Vaccines are thoroughly tested for safety before they're approved. They’re also continually monitored for safety and effectiveness.
Most
vaccine side effects are minor and go away within a few days. They may include fever, a sore arm, or a rash. Serious side effects are rare, but they can occur. These may include severe allergic reactions. However, these side effects are extremely rare, especially when compared to the health risks associated with the diseases these vaccines prevent.
