Immunization happens when a person becomes protected against a disease through vaccination. Getting vaccinated is one of the safest and most effective ways of preventing infectious diseases.
What is immunization?
When disease-causing viruses or bacteria (germs) invade the body, our immune systems are activated to attack them. Vaccines work by mimicking these germs so that if you are exposed to the real germ, your immune system is prepared to respond quickly.
Vaccines contain dead and weakened forms of germs or small pieces of germs. Others contain genetic instructions for immune cells to identify germs. Since vaccines do not contain germs in disease-causing forms, they will not give you the disease they are designed to prevent.
Most vaccines are given as an injection (shot). Side effects are usually mild, such as redness or soreness where the shot was given or a low-grade fever.
Why is immunization important?
Getting vaccinated is one of the most effective ways of preventing infectious diseases, disabilities, and deaths. In the United States, routine childhood vaccines prevent many diseases, and immunization has reduced the occurrence of most vaccine-preventable diseases by over 95%.
Adults need vaccines too, even if you got all your childhood shots. The protection for some shots can wear off over time, and as you get older you may be at risk for diseases like shingles. All adults should get a yearly flu shot and other vaccines based on age, job, lifestyle, travel, or health conditions.
Getting vaccinated also helps decrease the spread of diseases to other people. When enough people are vaccinated against a disease, it is more difficult for that disease to spread and cause an outbreak. People with serious allergies or weakened immune systems who can’t get vaccinated will also gain some protection from getting sick (known as community or herd immunity).
Are vaccines safe?
Vaccines are one of the safest ways to protect against many infections. Every vaccine is safety tested before it’s approved by the FDA and recommended for use by the Centers for Disease Control and Prevention (CDC). Vaccine manufacturers test each vaccine lot for identity, purity, strength, and sterility before they are released for use. The FDA and the CDC also monitor the safety of vaccines in infants, children, and adults after they come to market.
In the event of a public health emergency, the FDA may issue an Emergency Use Authorization (EUA) to facilitate the availability and the use of a vaccine. An EUA requires an FDA review of data on the quality and consistency of the vaccine product and a review of data collected from studies with people who volunteer to take the vaccine.
Where can I learn more?
To see if you or a family member should be immunized, review the immunization schedules at https://www.cdc.gov/vaccines/schedules.
If you or someone you know experiences an adverse event (side effect) after being immunized, report the event to the Vaccine Adverse Event Reporting System (VAERS) at vaers.hhs.gov/reportevent.html.
The FDA encourages diverse participation in clinical trials. If you think a clinical trial may be right for you, talk to your health care provider. You can also search for clinical trials in your area at www.ClinicalTrials.gov.
For more information on health equity, visit www.fda.gov/healthequity.