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How vaccines work
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How COVID-19 vaccines will work: what you need to know

With at least five companies working to get a COVID-19 vaccine on the market as soon as possible, you probably have questions about how vaccines work. So we went digging to find answers. Here’s what we found out.

Vaccine 101

Vaccines work with your immune system to help your body fight coronavirus in the event of exposure, by teaching it what to look for.

COVID-19 can be spread easily from person to person who are in close contact with each other (within 6 feet).

Also, when an infected person coughs, sneezes, breathes, sings or talks, respiratory droplets can cause infection when inhaled or deposited on mucous membranes that line the inside of the nose and mouth.

According to the CDC, there are now five clinical trials are in progress or being planned for COVID-19 vaccines in the United States. They are:

  1. AstraZeneca’s COVID-19 vaccine
  2. Janssen’s COVID-19 vaccine
  3. Moderna’s COVID-19 vaccine
  4. Novavax’s COVID-19 vaccine
  5. Pfizer’s COVID-19 vaccine​

How infections can make you sick

When bacteria or viruses invade the body, they attack and multiply and cause an infection. The body then releases white blood cells to fight the infection. The white blood cells are composed of three different types:

  • macrophages,
  • B-lymphocytes and
  • T-lymphocytes.

Macrophages kill invading and dead or dying cells and leave behind antigens. The body identifies
antigens and stimulates antibodies to attack them.

B-lymphocytes attack antigens left behind by the macrophages.

T-lymphocytes then attack the infected cells.

It can take the body several days to identify and use all the germ-fighting tools available to fight a germ. But the immune system remembers what it learned about how to fight a particular disease.

If the body encounters the same germ again, T-lymphocytes, also called memory cells, go
into action. 

How vaccines work

By imitating an infection, vaccines help the body develop an immunity to the disease. The imitation infection produces T-lymphocytes and antibodies.

Sometimes a vaccine causes minor symptoms such as a fever; they are normal and should be expected as the body builds up immunity. Most side effects of a vaccine are mild.

Once an infection disappears, it takes the body a few weeks to produce the T-lymphocytes and B-lymphocytes that will remember how to fight the infection.

Some vaccines may require more than one dose for the immune system to build up complete immunity to a disease. If protection from a disease begins to wear off, a “booster” dose may be needed to bring immunity levels back up.


A coming coronavirus vaccine will help our bodies develop immunity to the virus that causes COVID-19 without us having to contract the illness, which has caused 267,000 deaths in the United States as of Monday. Utah has reported 871 deaths as of Monday.

It is possible to get sick with coronavirus after vaccination because it normally takes a few weeks for the body to produce T-lymphocytes and B-lymphocytes after being inoculated.

Learn more about U.S. COVID-19 vaccine clinical trials here.

For more information on vaccines call 800-CDC-INFO (800-232-4636) or visit

How To Prevent the Spread of COVID-19 Coronavirus

COVID-19 coronavirus spreads person to person, similar to the common cold and the flu. So, to prevent it from spreading:

  • Wash hands frequently and thoroughly, with soap and water, for at least 20 seconds.
  • Don’t touch your face.
  • Wear a mask to protect yourself and others per CDC recommendations.
  • Keep children and those with compromised immune systems away from someone who is coughing or sneezing (in this instance, at least six feet).
  • If there is an outbreak near you, practice social distancing (stay at home, instead of going to the movies, sports events, or other activities).
  • Get a flu shot.

Local resources

KSL Coronavirus Q&A 

Utah’s Coronavirus Information 

Utah State Board of Education

Utah Hospital Association

The Church of Jesus Christ of Latter-day Saints

Utah Coronavirus Information Line – 1-800-456-7707

National Resources

Centers for Disease Control and Prevention

Commonly asked questions, World Health Organization

Cases in the United States

Why is KSL NewsRadio covering this?

We have a lot of questions about the vaccines currently being tested for COVID-19, and we know you do, too. We wanted to provide answers to those questions. Each day this week, we'll be diving deep into a different aspect of vaccine development and distribution to help all of us learn more about the process.

Where did the idea come from?

It came from you! Listeners like you frequently ask us questions or send us ideas for future stories.

How did KSL report the story?

We went directly to the source of information wherever possible to obtain the facts about the vaccines currently in development, which in this case meant consulting with the Centers for Disease Control.

I have an idea for a future in-depth report. How do I tell you about it?

We would love to hear your ideas. You can email our team at If you are hoping to reach a specific member of our team, you can also contact them directly through our bios, here.