Immunization is a key measure to protecting individuals and communities from infectious disease. It is a process that helps people to build immunity—protection from an infectious disease—by introducing a substance to the body that prompts a response from the body’s immune system. The immune system is the body’s natural defense against infectious bacteria, viruses and toxins.
COVID-19 Vaccines
Different vaccines work in different ways, but essentially each vaccine does the same thing: it shows your body’s immune cells an antigen—a toxin or other foreign body like a virus or part of a virus—and the immune cells tell your body to build defenses by making your body’s natural defense against disease—your immune system—even stronger. This prompts your body to make antibodies and infection-fighting cells to fight the virus or bacteria. The antibodies stay in your blood and protect you in case you are infected with the real virus.
People—and animals—can be immunized through different methods, including oral methods (by mouth), intranasal sprays (in the nose), and most commonly, injection.
There are several types of vaccines including the following:
Learn more about the different types of vaccines here.
In the United States, vaccine development and production is monitored by the U.S. Food and Drug Administration (FDA). Vaccines must undergo a rigorous process to test their safety and efficacy, which includes lab studies, clinical trials, and extensive review of all lab and clinical trial data before any vaccines can be administered to the public. Once all these steps are completed, the FDA may issue formal approval of the vaccine. Next, all data must be reviewed by medical and public health experts at the Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC). If the data show that the vaccine is safe and effective, ACIP will supply their recommendation for the addition of the vaccine to the recommended vaccine schedule. The CDC then reviews and approves the recommendation.
Learn more about the Journey of a Vaccine
Under certain emergency circumstances, the FDA may provide authorization for use of a vaccine within certain populations of the public before the vaccine has received formal approval. This is called an emergency use authorization (EUA). During public health emergencies, like the COVID-19 pandemic, the FDA may choose to issue an EUA to make medical countermeasures, such as vaccines or treatments, available to the public.
Flu viruses (influenza) change often and during any given year, different strains, or versions of the virus may be more common than in other years. Each year’s flu vaccine is formulated to match the strains that are most likely to be present. This means that you need to get a different formulation each year to ensure you get the most protection possible from that year’s most common strains. Learn more
Receiving the right vaccinations at the right times throughout your life is the key to protecting your health from vaccine-preventable illnesses. Most people receive the majority of their vaccines as an infant or toddler, which helps provide protection before they are exposed to vaccine-preventable diseases. However, over the course of your life, you will need to receive some vaccinations annually, like the flu vaccine, or at multi-year intervals, like the vaccine for tetanus every 10 years. This is where the U.S. recommended vaccine schedule comes into play. The vaccine schedule helps the public and providers—like your doctor—know which vaccines to recommend and when.
Medical and public health experts with ACIP recommend standardized vaccine schedules for infants, children, youth, and adults, which are approved by the CDC, the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP). These are the same schedules that your doctor, or your child’s pediatrician, uses when recommending vaccines for you and your family.
Open each section below to learn more about which vaccines should be received and when to help you and your family stay protected. See the Immunization Schedules page on the CDC website for detailed information or use these handy assessment tools for adults and children. Answer a few questions to find out what vaccines your or your child needs.
Content in this section adapted from materials created by the CDC.
Medical and public health experts with the Advisory Committee on Immunization Practices (ACIP) recommend that people follow standardized vaccine schedules for infants, children, youth, and adults. These schedules are determined by ACIP and approved by the Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP). This is the same schedule that your doctor or your child’s pediatrician uses when recommending vaccines for you and your family.
Following the vaccine schedule and staying up to date on recommended vaccines is the best way to protect yourself and your loved ones from severe illness and other complications caused by vaccine-preventable diseases.
“Immunization: The Basics,” Centers for Disease Control and Prevention, last modified September 1, 2021, https://www.cdc.gov/vaccines/vac-gen/imz-basics.htm
“Vaccine Types,” U.S. Department of Health and Human Services, Office of Infectious Disease and HIV/AIDS Policy (OIDP), last modified April 29, 2021, https://www.hhs.gov/immunization/basics/types/index.html
“Vaccines for Your Children,” Centers for Disease Control and Prevention, last modified March 19, 2019 https://www.cdc.gov/vaccines/parents/index.html
“Vaccines and Immunizations,” Centers for Disease Control and Prevention, last modified February 16, 2021, https://www.cdc.gov/vaccines/
“Growing Up with Vaccines: What Should Parents Know?” Centers for Disease Control and Prevention, last modifed July 2018, https://www.cdc.gov/vaccines/growing/images/global/CDC-Growing-Up-with-Vaccines.pdf
Find out how getting routine vaccinations on time and staying up to date helps protect us, our families, and our communities from potentially life-threatening diseases.
