COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without us having to get the illness. When you get the vaccine, your immune system makes antibodies and other infection-fighting cells that protect you in case you are infected with the virus.

How do the Moderna and Pfizer vaccines work?

Vaccines that have been authorized from Pfizer and Moderna are mRNA vaccines. mRNA vaccine technology has been studied and worked with for decades.

There is no virus in the mRNA vaccines, so you cannot get a COVID-19 infection from the vaccine. Instead, mRNA vaccines give our cells instructions to make a harmless protein—one that looks just like an important protein on the COVID-19 virus. When your cells make that protein, your body creates a strong immune response and antibodies to protect against COVID-19. Your body learns how to protect you from getting infected without exposure to the virus.

After the mRNA teaches our cells to protect against COVID-19, our body’s enzymes quickly break down and eliminate the mRNA. mRNA does not get into the nucleus of our cells, DNA, or genetic material.

Although these are the first mRNA vaccines to be authorized for use, mRNA technology has been studied for more than 30 years. More information about how mRNA vaccines work can be found on the CDC’s website.

How does the Johnson & Johnson vaccine work?

The Johnson & Johnson COVID-19 vaccine uses a harmless form of the common cold virus (not the coronavirus) that’s been modified so that it can’t make you sick. This harmless virus delivers instructions to teach our cells to make a protein found on the surface of the coronavirus. When your cells make that protein, your body creates a strong immune response to protect against COVID-19. Your body learns how to protect you from getting infected with COVID-19 without exposure to the actual coronavirus.

This type of vaccine cannot infect you with COVID-19 or with the harmless common cold virus used to deliver the instructions. The vaccine does not get into or change the nucleus of our cells, DNA, or genetic material.

Scientists began creating viral vectors in the 1970s. For decades, hundreds of scientific studies of viral vector vaccines have been done around the world. They have been used against other infectious diseases like Ebola, Zika, flu, and HIV.

Women younger than 50 years old should be aware of the risk of a very rare but serious condition involving blood clots and low platelet counts. Other COVID-19 vaccines (Pfizer and Moderna) are available that do not have this risk.

If you haven’t already been vaccinated, you can find out where to get your vaccine and find answers to your questions at www.kingcounty.gov/vaccine.

Find out more in the Frequently Asked Questions about COVID-19 vaccine section of the Public Health – Seattle & King County website.