What you need to know
- We develop immunity—protection from infection—when our immune systems recognize a particular virus, bacteria, or fungus and destroy it.
- Immunity helps us resist and fight diseases and protects us against becoming seriously ill, but it’s not perfect.
- Staying up to date on routine vaccines is a safer way to build immunity than getting infected with any disease.
The immune system is a network of organs, cells, and chemicals that helps our bodies fight off germs. Decades of research show that vaccines are the safest, most effective way to strengthen our immune systems by teaching our bodies how to recognize and attack invaders. Since some invaders mutate quickly, we need updated vaccines to stay protected.
Unfortunately, vaccination rates are declining—especially among children—leaving everyone more vulnerable to infection. Plus, now that kids are back at school, they’re more likely to become sick and bring germs home.
Read on to learn more about what immunity is and how vaccines help us build protection.
What is immunity?
We develop immunity—protection from infection—when our immune systems recognize a particular virus, bacteria, or fungus and destroy it.
In utero, babies acquire passive immunity to certain infections from antibodies (protective proteins) from their birthing parent through the placenta. After birth, babies get antibodies from breast milk. Passive immunity only lasts for a few weeks or months.
We acquire active immunity when we’re exposed to germs, either by getting infected or by getting vaccinated, which teaches our bodies how to fight off future infections. If you’ve had an illness or you’ve been vaccinated against a particular disease, you could get infected again but still be protected from developing the worst, and sometimes deadly, symptoms.
This is especially true if the pathogen causing the disease mutates quickly, like the viruses that cause COVID-19 and the flu. That’s why we need updated COVID-19 and flu vaccines to target newer variants.
What is herd immunity?
Herd immunity, also known as community or population immunity, occurs when enough people have immunity against a disease to dramatically reduce the spread. For example, diseases like measles, mumps, and rubella are rare in the U.S. because we’ve achieved herd immunity through mass vaccination.
Herd immunity protects all of us, especially infants and children who are too young to be fully vaccinated and adults who are unable to get vaccinated.
Recent outbreaks of measles and other vaccine-preventable diseases are attributed to a decline in vaccination rates, which jeopardizes herd immunity.
How do vaccines help our immune systems fight off infections?
Vaccines teach our immune systems how to recognize invaders and attack them before they make us seriously ill. Since some viruses mutate quickly and evade our immunity, we need updated vaccines to help us stay protected.
This season’s COVID-19 and flu vaccines are available now and specifically target current variants. They are recommended for everyone 6 months and older.
Find pharmacies near you at Vaccines.gov.
For more information, talk to your health care provider.
This article is supported by the Centers for Disease Control and Prevention of the U.S. Department of Health and Human Services (HHS) as part of a financial assistance award to the CDC Foundation totaling $69,392,486 with 100 percent funded by CDC/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by CDC/HHS, or the U.S. Government. In addition, the CDC Foundation does not guarantee and is not responsible for the accuracy or reliability of information or content contained in this article. Moreover, the CDC Foundation expressly disclaims all liability for damages of any kind arising out of use, reference to, or reliance on any information contained within this article. This article are not intended as, and should not be interpreted by you as, constituting or implying the CDC Foundation’s endorsement, sponsorship, or recommendation of the information, products, or services found therein.