General Vaccine Information

Infectious diseases are spread from one person to another, usually through very small organisms called bacteria or viruses (“micro”-organisms). These microorganisms reproduce in their host, often making them sick and then spread to the next unlucky person. The first time someone's immune system meets a new bacteria or virus, it works very hard to create the best possible tools to destroy that particular microorganism. Generally, these tools are called antibodies and copies of them are kept stored away in the body so if the immune system ever sees that bacteria or virus again, it’s much easier to fight off. This is called gaining immunity, and it’s the reason a person who has already been sick with a particular disease usually won’t get sick from it again.

Vaccination, or immunization, offers us a way to create immunity and prevent serious illness without ever being exposed to the real microorganism. A vaccine contains pieces of bacteria or viruses, or whole but non-functional bacteria or viruses. A person can’t catch the disease from the vaccine, but their immune system doesn’t know that. It responds to the vaccine the same way it responds to a real threat and it makes antibodies just like it would if it encountered the real bacteria or virus The important difference is, the person doesn’t get sick and can’t spread a disease to anyone else.

Read more about vaccines and immunization.

Some common questions people have about vaccines are:

Are vaccines safe?

Yes! All vaccines have been rigorously tested for safety and effectiveness by doctors and scientists around the world. Read more about vaccine safety testing

Will vaccines make me sick?

While a vaccine cannot make you sick with the bacteria or virus it contains, some people may experience some flu-like symptoms due to the immune response caused by the vaccine. These are typically mild and go away after a few days. Read more about specific vaccine side effects.

Also, it takes the immune system a couple of weeks to create immunity after vaccination, and it is still possible to contract the disease during that time.

Who needs vaccines?

While infants and children are at the greatest risk from infectious diseases and therefore need them the most, people of all ages can benefit from the protection vaccines offer. See our Resources for Children, Adults and Pregnant Women page for more information.

Where do my family and I get vaccinated?

The best place to get vaccinated is at your doctor’s office. If you don’t have doctor, you can search for a clinic or pharmacist who can give you your vaccine. If you are uninsured or your insurance doesn’t cover vaccines, see our list of vaccination clinics.

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