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How will a vaccine help with COVID-19 herd immunity?

(PHOTO: AP Photo/LM Otero)

EDITORIAL NOTE: ‘How will a vaccine help with COVID-19 herd immunity?’ is the fourth part of our four-part series, ‘The Vaccines: Hope on the Horizon.’ Each day, KSL will break down a different aspect of COVID-19 vaccine development and distribution. Listen to Utah’s Morning News at 7:45 a.m. and to Jeff Caplan’s Afternoon News at 4:45 p.m. every day this week for the latest. 


SALT LAKE CITY – Herd immunity happens when a large percentage of people develop immunity to a disease either through vaccination or infection. 

Dr. Shankar Swaminathan, the Chief of the Infectious Disease Division at University of Utah Health, asks people to imagine that a person with COVID-19 typically infects two people. 

“Let’s say that half the people are immunized. So, now, if you have it and you run into two people, on average you’re going to infect one person instead of two,” Swaminathan says. 

Although approval of a COVID-19 vaccine may be just around the corner, it’s unclear how many people would need a shot to achieve herd immunity in Utah. 

However, Dr. Swaminathan says the more people who are immunized, the greater the chances of achieving herd immunity. 

“Let’s say two out of three people get vaccinated. Now…you’re able to spread it to less than one person,” Swaminathan says. “On average, the disease is going to start dying out.”  

The best guesses range anywhere from 70% to above 90% immunity to get to herd immunity.

Don’t try and catch COVID-19 to speed up herd immunity

Dr. Tamara Sheffield, the Medical Director of Community Health and Prevention at Intermountain Healthcare, says people who have recovered from COVID-19 do have immunity to it. 

“Those who have the severest disease tend to also have the greatest amount of immune protection. But we don’t know how long that will last,” Sheffield says.  

Those are some of the reasons she asks people not to try and catch COVID-19. She also reminds people that they cannot know for sure how their bodies will react to the virus. 

It will take time

Dr. Mark Oliver, the Head of Infectious Disease at St, Mark’s Hospital in Salt Lake City, agrees with following public health guidelines. 

However, he also believes the immunity COVID-19 patients acquire will play a role in achieving herd immunity. 

“We are encouraged that a combination of vaccination plus ongoing infection in the community will get us to that magic percentage that we call herd immunity,” Oliver says. 

Especially because we do not know enough about the vaccine yet.  

“We really won’t know for a year or more if the vaccine gives better protection than native infection. Also, how long lasting the immune response will be from the vaccine is still a big question mark. Is this a vaccine [where] you’re going to get two shots and be protected with 95% certainty for the rest of your life? Or is this a vaccine that we’re going to have to get another booster at six months or a year or two years?” Oliver says.   

But Dr. Oliver also says if a vaccine is safe and effective, getting one will help protect people who cannot take it for health or other reasons. 

Dr. Sheffield says vaccines also tend to be more effective than any acquired immunity. 

“Vaccines…tend to provide a fairly consistent level [of immunity], and sometimes a higher level, than having had a disease or being exposed to a disease. We will also, though, have to watch over time to see how long that protection lasts,” Sheffield says.         


How To Prevent the Spread of COVID-19 Coronavirus

COVID-19 coronaviruses transmitted from person to person. It is a virus that is 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.
  • Wear a mask.
  • Don’t touch your face.
  • 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.

Where did the idea come from?

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.

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. In this case, that included the Utah health leaders who are responsible for making critical vaccine storage and distribution decisions.

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.