SALT LAKE CITY (ABC4) — The COVID-19 vaccine is very new at this point, so it might seem strange to compare it to the flu vaccine, which has been around for nearly a century.

Chances are the COVID-19 vaccine most people will be receiving this year, will not be their last. But whether or not the COVID-19 vaccine will need to be administered to people yearly, is simply not known at this point.

“There’s not a good answer for that just yet. The vaccine simply hasn’t existed long enough to determine how long immunity lasts, and we also haven’t had the virus itself around long enough to determine whether or not there are going to be different strains that circulate each year similar to influenza,” Tom Hudachko, Director of Communications at the Utah Department of Health, says.

That’s why the flu shot changes each year, he says. The flu has been around long enough to have created different strains, and therefore, the vaccine has to be tweaked each year to keep up with them.

Dr. Andrew Pavia, an Infectious Disease Specialist at University of Utah Health, agrees that it’s too early to tell at this point how often people may need to receive the COVID-19 vaccine, but he says the need for future COVID-19 vaccines is likely.

“It looks like the vaccines produce a longer immune response than natural infection, so it may last longer than a year, but it’s unlikely to be permanent the way two doses of measles vaccine is,” he says. “So at some point, it’s likely that we will need to boost people, but we don’t know how frequently that will need to be.”

So how will experts figure out how long the effects of the COVID-19 vaccine last? The Centers for Disease Control and Prevention will have to figure out vaccine effectiveness based on how long it’s been since a person’s last dose, Dr. Pavia explained.

“Over time, we’ll see if we’re still getting 90 to 95 percent protection among people who were vaccinated in December 2020 and January of 2021,” he says.

He says there are two things to consider when thinking about the vaccine becoming less effective with time:

  1. Time- people lose antibody from the vaccine over time
  2. The emergence of new variants

Dr. Pavia says that viruses make variants all the time because they don’t make faithful copies of themselves. Most variants disappear, but the ones that stick around can spread.

“Over time, what the virus will need to do to survive is infect people that have been vaccinated. If variants occur naturally where the virus is more able to infect people who’ve been vaccinated, then we’ll start to see those variants spread more easily,” he says.

That’s what happens with the flu, and that’s why flu shots are different year to year. They adapt to keep up with new strains. However, the nature of the flu makes it far more likely to create new strains than COVID-19.

“So flu is uniquely adapted for rapid change. Coronavirus not so much, but like all viruses over time, it will change,” Dr. Pavia states.

He says it is likely that over time the virus is going to start to change in ways that make it more resistant to the current vaccine.

“Then we’re going to have to tweak the vaccine just like we do with the flu vaccine, but probably not every year,” he says.