What are vaccines, and how do they work?

Vaccines are made using a small amount of weakened or killed viruses or bacteria or from small parts of them. They are designed to help the body's immune system to build immunity or protection against the disease. When a person is infected with the virus or bacteria in the future, the immune system “remembers” and can quickly make antibodies to help fight the infection.

Why are vaccines important?

• Vaccines prepare your body to immediately recognize and destroy viruses and bacteria before they are able to make you very sick or cause death.
• In the United States, children are routinely vaccinated against 16 diseases that are especially dangerous for infants and young children.
• Before these vaccines were invented, children routinely died or became permanently disabled by these infections.
• Vaccines are so effective that we don't see these infections as much as before, but there are still outbreaks. The more people who are vaccinated, the better protected we all are, especially those most at risk.

Are vaccines safe?

YES

• Vaccine safety is incredibly important. Before they become available, vaccines are tested in thousands of volunteers to make sure they don't cause serious side effects. Once licensed and widely used, they continue to be closely monitored for extremely rare side effects that might occur in fewer than one in a million patients.
• Most children do not have any reaction to vaccines, but they can occur.
• Serious reactions, such as a severe allergic reaction, are rare but can occur.
• Vaccine additives are materials that are added to vaccines so they work and are safe.
• Each vaccine additive serves a purpose, such as to help the body recognize the bacteria or viral particle or to keep the vaccine from spoiling and making you sick.
• Vaccines are becoming purer and simpler, with fewer additives over time as technology advances.

Who makes the vaccine schedule, and when does my child need vaccines?

• The vaccine schedule is updated yearly by a panel of experts from the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AAFP), the Advisory Committee on Immunization Practices (ACIP), and the Centers for Disease Control and Prevention (CDC).
• At each checkup, your child's doctor will discuss what vaccines are due and why they are important.
• You can learn what vaccines are due at each visit on the CDC's website.

Where can I learn more about vaccines?

• The CDC vaccine website provides up-to-date information on vaccine schedules and how vaccines work.
• For city-specific information about COVID-19 in Chicago, including current statistics, updates, and vaccination resources, visit the City of Chicago COVID Dashboard.

How can I get my child or other family members vaccinated?

• Chicago Department of Public Health (CDPH) walk-In immunization clinics provide vaccinations for children 0 through 18 years of age at no out-of-pocket cost. Currently, we provide standard vaccinations to uninsured, underinsured, Medicaid (Title XIX) insured and Children’s Health Insurance Program (CHIP) individuals, as well as flu and COVID-19 vaccines to all Chicago residents eligible for these vaccines, regardless of insurance status.
• You can also use our resource finder to locate other vaccine resources near you.