A doctor answers questions about COVID-19 immunity, additional boosters and more

People wait in line for a COVID-19 vaccine.
People wait in line at a walk-up vaccination site in Washington, D.C. in November 2021.
Jim Watson | AFP via Getty Images 2021

The omicron surge is receding, but Minnesota is still logging thousands of COVID-19 cases daily. Our youngest kids still can’t get vaccinated, and there’s confusion about boosters.

Mayo Clinic preventive medicine physician Melanie Swift joined host Cathy Wurzer to answer your COVID-19 questions.

Use the audio player above or read the below transcript for the full conversation.

The surge appears to be ebbing, but are we out of the woods yet?

We’re on the downhill side of this hill. We haven't hit the bottom yet, but I think it's pretty clear that we're heading in the right direction.

What do you think of research on long-COVID-19 that seems to show that there can be serious long-term issues even in patients who were not hospitalized?

Long-COVID has been with us since the beginning, and I think we still are yet to see where it's going to land with omicron. But we do know that even in mild cases, people can experience some of those symptoms for many months after they've had COVID – up to a third to a half of people could have some symptoms, typically fatigue.

I would say, though, that the brain fog is really different from something that you'd see in a dementia. Brain fog might be forgetting where you put your car keys, but dementia would be forgetting how to use those keys. It’s a very different thing and not as severe as a dementia. It's just more feeling a little bit fuzzy and not operating as quickly as you normally do. And that does happen with mild cases.

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The omicron surge we do expect may create a surge in late effects as well.

The sister variant of omicron is now really racing through the population. What does that mean?

This variant is called BA.2. It doesn’t look like it is going to be significantly different in terms of how well vaccine protects you. You still need a booster to be well protected.

It doesn't look like it is making people sicker than the omicron that we've come to know these past few weeks. What it looks like it may do is sort of slow the slope of that descent, so that it doesn't go immediately away. But really, we're not thinking that this is going to be clinically really any different.

If you’ve recently have COVID-19, is it true that you have immunity for 90 days?

Yes, [but] you can still get COVID within 90 days of prior infection. It is highly unusual within 30 days. And generally, we don't see it within 45. But we have seen it occasionally. I've seen people reinfected as recently as three or four weeks later, but that is really unusual.

For the most part, people have good levels of protection against a repeat infection within those three months, but it does wear off during the course of that time.

Does someone who is vaccinated, boosted and gets COVID-19 have ‘super immunity’ for a bit?

Kind of. There is this temporary protection from having infection, and there's definitely protection from being vaccinated and boosted. And that protection is going to last between three to six months depending on how healthy your immune system is. By having both of those things, the rate of a subsequent infection is much lower. So, a little bit “super immune” for a few months.

Will we have to get another booster?

Like many things, the COVID crystal ball isn't perfectly crystal clear on that point. Those studies are going on now. We do have some evidence that our body's immune cells that make antibodies have learned how to make it and will maintain that memory for some time.

So it may be that after a booster or two, we will have longer lasting protection. The problem, though, even if that holds true is that mutations will continue to occur. We’ll end up still getting variants as long as this is transmitting. So ultimately, we are likely to not be protected forever from these first couple of boosters and will need some tweaking later — much like we do with flu vaccines where we have to get boosted once a year with different strains.

When does a mutation become a variant? And when does a variant become a variant of concern?

Mutations are basically mistakes in your body's reading and reproducing the genetic code of the virus. Think of this RNA that viruses are made of is like a recipe — it's the instructions.

What our bodies do is read that recipe and create copies of it. But just like if you're copying out a recipe by hand, you might misspell a word from time to time. Or if you're typing it, you might put in an extra space. Each one of those in the genetic code is a mutation, but most of them are not important.

If you misspell the word flour in your muffin recipe, the next batch of muffins will probably come out about the same. But it becomes a variant when there's a cluster of these changes that starts to repeat reproduce itself over and over again and becomes basically — now it's a pumpkin muffin instead of your corn muffin, or whatever. Those variants get established and get transmitted, and they may not be any worse than the original version.

It becomes a variant of concern when one of a few different things happen that make this dangerous: It may cause more severe disease, it may be easier to transmit to other people. Or it may be that our protections don't work — our tests won't pick it up; our vaccine doesn't protect us against it; or it's not susceptible to the treatments that we have.

Any of those things could make it rise to the level of a variant of concern. And right now, we just have two variants of concern in the U.S., and that's delta and omicron.

How long are you contagious with COVID-19?

The contagiousness tracks to some degree with the amount of virus that is present in your upper airway. We know that we can detect that virus a little bit longer than people actually spread it to other people — so it's the amount that you have, not just the fact that it's there.

For most people, they no longer are contagious at around the eight-day mark after symptom onset. It’s not a light switch that goes off. It's a dimmer switch. You get less and less contagious, and some people are not contagious after five or six days. Other people might be a little bit contagious out to 10 days.

There are exceptions to that – people who have really severe infections or are in the hospital for it might be contagious longer. People who are immunosuppressed might be contagious longer. Those symptoms, however, may linger on long after you're not contagious anymore.

So for someone who's got a healthy immune system and has an infection, 10 days after their symptoms began, they can consider themselves not contagious anymore, but they may continue to have lingering symptoms for some weeks.

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