How do COVID-19 vaccines work?

The Pfizer and Moderna vaccines use messenger RNA or mRNA, to trigger the immune system to produce protective antibodies and memory cells against the coronavirus. These are the first vaccines to use mRNA. It is important to note that neither of these vaccines uses the coronavirus itself, and neither can cause COVID-19.


The Johnson & Johnson vaccine is a vector vaccine. That means it contains a weakened version of a virus that causes the common cold that is different from the coronavirus. The cold virus is modified to carry information about the coronavirus to the body. This vaccine causes the body to make a protein that is unique to the coronavirus. This prompts the immune system to produce protective antibodies against the coronavirus. Like the Pfizer and Moderna vaccines, this vaccine does not use the coronavirus itself, and cannot cause COVID-19.


None of the vaccines affect a person’s DNA. They also do not cause coronavirus.

Show All Answers

1. Is the COVID-19 vaccine safe?
2. What are the ingredients in the COVID-19 vaccine?
3. How do COVID-19 vaccines work?
4. Which COVID-19 vaccine should I get?
5. How long does it take to be fully protected after receiving the vaccine?
6. Will I have a positive COVID-19 test after getting the vaccine?
7. Do I still need to wear a mask after getting the COVID-19 vaccine?
8. If I’ve been vaccinated and was exposed to someone who has COVID-19, do I need to quarantine?
9. Can the COVID-19 vaccine help me even if I've already been affected by COVID-19?
10. Can I get my flu shot at the same times as my COVID shot?
11. Can women who are pregnant get the COVID-19 vaccine?
12. Why was I told to wait a month after getting the vaccine before getting a mammogram?
13. How do COVID-19 vaccines protect the community?
14. Does the vaccine have any side effects?
15. What is V-safe?
16. How much does the vaccine cost?
17. Are the vaccines FDA approved?
18. How were the vaccines tested?