How do COVID-19 vaccines work?

Coronavirus (COVID-19) Resources

How COVID-19 Vaccines Work?

Vaccines help our immune system fight infections in the future. COVID-19 vaccines will protect us from the virus that causes COVID-19 without having to get the illness.

It typically takes a few weeks after the last dose in a series to become fully protected. On the days after taking the vaccine, you may have a sore arm, aches, fatigue or fever, but these are not harmful. These symptoms signal that your immune system is developing protection from the virus.

The first two vaccines that are out are not live virus vaccines. This means that they cannot give you COVID-19. After getting the vaccine, you will not shed live virus around your home or put others in your household at risk of COVID-19 disease. The vaccine will not affect a PCR COVID-19 test.

The first two vaccines were made using mRNA technology. mRNA stands for messenger ribonucleic acid. mRNA is not able to alter or modify a person’s genetic makeup (DNA). Learn more about mRNA vaccines at CDC: Understanding mRNA COVID-19 Vaccines.

These vaccines do not contain a preservative. They do not contain gelatin.

For more information about ingredients found in vaccines, check out the FDA website. For specific concerns about certain ingredients, get factual information from Children’s Hospital of Philadelphia: Vaccine Education Center or Immunization Action Coalition: Talking About Vaccine.