Vaccines protect you from infectious diseases that can make you sick, cause serious complications and sometimes are life-threatening. They also reduce the number of people who get so sick that they need to be hospitalized. And they help keep disease from spreading in communities and around the world.
A vaccine is a live or inactivated substance that causes your immune system to produce antibodies against a specific pathogen. The vaccine contains antigens, which are usually weakened or killed bacteria or viruses. It may also contain adjuvants, which enhance the immune response, and stabilizers, which prevent the active ingredients from breaking down or changing during manufacturing and storage.
The vaccine production process can take up to two or more years, and is carried out in several stages. During the pre-clinical phase, government, academic and industry researchers test the vaccine candidate on cells, tissues and animals to find out if it promotes an immune response without making the animal sick. If the vaccine looks promising, it goes to the clinical trial stage, where thousands of volunteers receive different doses to test safety and efficacy.
Vaccines are delivered by needle injection (immunization) into your arm, thigh, leg or belly button. Your healthcare provider will first clean the injection site with an alcohol swab. Most vaccines are administered intramuscularly, because some immune cells are located in the muscles of your body. Some are administered orally, and others — such as the tetanus vaccine — are given as a shot under the skin.
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