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

Nov 30, 2020, 3:33 PM | Updated: 4:03 pm

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

We want to hear from you.

Have a story idea or tip? Send it to the KSL NewsRadio team here.

Today’s Top Stories


FILE - A doctor loads a dose of Pfizer COVID-19 vaccine into a syringe, Thursday, Dec. 2, 2021, at ...
Aimee Cobabe

Bill banning vaccine passports heading to Utah Senate

A bill to ban vaccine passports is heading out of the Utah House and into the Utah Senate. The bill is similar to a failed bill from 2022.
3 days ago
A bill on transgender healthcare — banning transgender-related surgeries and puberty blockers for...
Eliza Pace, KSL TV and Aimee Cobabe, KSL NewsRadio

Utah Senate approves changes to transgender care bill, passes on to Gov. Cox

SB16 bans gender-confirming surgeries for minors and also places a moratorium on puberty blockers for minors.
6 days ago
Havasu Falls spills into the water pools below in Supai, Arizona, in October of 2016. Photo credit:...
Forrest Brown, CNN

Grand Canyon’s Havasu Falls to reopen to visitors after 3-year closure

 (CNN) — Havasu Falls, one of the most intriguing features of the Grand Canyon system, will be reopening to visitors after a three-year closure caused by the Covid-19 pandemic. But it’s with a catch. The reopening is scheduled for February 1; however, access will be limited initially to a certain, small group. People whose previous […]
6 days ago
White carnations representing each of the 1,746 unborn babies that were aborted in Utah in 2022 are...
Allessandra Harris and Simone Seikaly

Speeches, silence, during Pro-Life Utah memorial at the Capitol

About 100 people including Utah lawmakers and religious leaders attended the memorial on Wednesday, Jan. 25, 2023.
7 days ago
 A mental health clinic will reopen on Thursday after a carbon monoxide leak sent at least 17 peop...
Michael Locklear

Carbon monoxide poisoning at central Utah clinic hospitalizes 17 people

The Central Utah Counseling Center in Ephraim was evacuated a week ago after a problem with an old furnace was discovered.
8 days ago
a row of guns are pictured...
Mark Jones

KSL at Night: How do we solve gun violence?

KSL at Night hosts Taylor Morgan and Maura Carabello speak with Clark Aposhian, chairman of the Utah Shooting Sports Council about gun violence.
9 days ago

Sponsored Articles

Banner with Cervical Cancer Awareness Realistic Ribbon...
Intermountain Health

Five Common Causes of Cervical Cancer – and What You Can Do to Lower Your Risk

January is National Cervical Cancer Awareness month and cancer experts at Intermountain Health are working to educate women about cervical cancer, the tests that can warn women about potential cancer, and the importance of vaccination.
Kid holding a cisco fish at winterfest...
Bear Lake Convention and Visitors Bureau

Get Ready for Fun at the 2023 Bear Lake Monster Winterfest

The Bear Lake Monster Winterfest is an annual weekend event jam-packed full of fun activities the whole family can enjoy. This year the event will be held from January 27-29 at the Utah Bear Lake State Park Marina and Sunrise Resort and Event Center in Garden City, Utah. 
happy friends with sparklers at christmas dinner...

15 Easy Christmas Dinner Ideas

We’ve scoured the web for you and narrowed down a few of our favorite Christmas dinner ideas to make your planning easy. Choose from the dishes we’ve highlighted to plan your meal or start brainstorming your own meal plan a couple of weeks before to make sure you have time to shop and prepare.
Spicy Homemade Loaded Taters Tots...

5 Game Day Snacks for the Whole Family (with recipes!)

Try these game day snacks to make watching football at home with your family feel like a special occasion. 
Happy joyful smiling casual satisfied woman learning and communicates in sign language online using...

The Best Tools for Deaf and Hard-of-Hearing Workplace Success

Here are some of the best resources to make your workplace work better for Deaf and hard-of-hearing employees.
Team supporters celebrating at a tailgate party...

8 Delicious Tailgate Foods That Require Zero Prep Work

In a hurry? These 8 tailgate foods take zero prep work, so you can fuel up and get back to what matters most: getting hyped for your favorite
How COVID-19 vaccines will work: what you need to know