COVID-19 boosters. They were introduced to the public a couple of months ago, but for many people, there is still a lot of confusion over what they are and who needs them.

As we approach the holiday season, when many people will reunite with family and friends they may not have seen for over a year, having as much protection for themselves and their loved ones is a priority. But who should get a booster? And which one should they get?

North Carolina Health News sat down with Cameron Wolfe, associate professor of medicine at Duke University School of Medicine, who specializes in infectious diseases, to ask all of your questions. Answers may be edited for grammar and brevity.

NC Health News: What is a booster shot, and why do some people need it?

Cameron Wolfe: The concept is simple — can I top up your immune system’s defense, which naturally over time tends to wane. What we’re seeing with COVID is, unfortunately, the vaccines, like most other vaccines, do tend to have diminished benefit over time.

Folks who are either older and have an immune system that tends to be what we call immunosenescence, or just a little bit more stagnant and forgetful. They tend to lose their defenses a little quicker. 

Same is true for folks who are immunosuppressed. 

When you then combine those things together with folks who are either exposed more frequently to COVID, for example, health care workers, or folks who have greater risk if they were the unlucky one or two who have diminishing immunity, who’s going to get more severe cases, this idea of saying “Hey, maybe there’s a subsection of community who really can help bolster their defense.” 

The idea is simple enough. It’s that across the whole population, there’s different paces at which our defense wanes, and can we find certain people there who need a top up. That’s not really different than what we do each year for flu vaccines, it’s what we do with pneumonia vaccines. 

Wolfe said confusion was generated when Pfizer applied for Food and Drug Administration approval for booster shots for all people. Instead, the FDA authorized booster doses for people 65 years and older, people 18-64 years old at high risk of severe COVID-19 and people 18-64 years old whose frequent exposure to COVID-19 puts them at higher risk.

Pfizer is applying for approval for a booster dose for everyone again.

As of Oct. 21, the Centers for Disease Control and Prevention issued new guidelines for booster shots. Those who received a Pfizer of Moderna vaccine are eligible for a booster six months or more after vaccination if they are:

The CDC recommended a booster shot for those who are 18 and older who got the Johnson & Johnson vaccine two or more months ago.


NCHN: What is a valid pre-existing condition for a booster shot? Do mental health conditions count? What does it mean to be immunocompromised?

Wolfe: I’m not sure that mental health has ever come into the direct considerations here only because we would expect their immune system to be just as functional as any one of their age-appropriate peers —  not to say getting COVID or the worry of getting COVID isn’t a real issue. 

This is where we need to make a separation between purely immunosuppressed individuals and the rest of the at-risk group. 

Let’s take Pfizer, for example. There’s two doses in a regular course. When you were vaccinated, however, a few months ago, you would have had a first dose and three weeks later a second dose. There are certain sections of folks who are immunosuppressed, who we know that their defense and their response to that vaccine was not as good as the general community. That is true of people who are at least moderately to highly immunosuppressive — transplant patients, people getting chemotherapy, patients with advanced HIV – there’s a small group, we think about two to three percent of the population fall into that category. They’ve already been independently focused on and they’ve been given three doses in their original course. The way I tend to think about it is someone who’s immune suppressed, their initial course is three doses, not two.

Boosting is a separate sort of group. Boosting is you had a great response originally whether it was to two doses or three, but over time, your defense has faded.


Let’s think about either the elderly, whose defense fades more rapidly, or people in whom a breakthrough infection would be more critical such that they’re at high risk of a bad outcome. And that includes all the other reasons why people get sick with COVID — obesity, diabetes, heart and lung disease. 

Then there’s a third section, groups of people who are just so repetitively exposed to COVID that their risk of a breakthrough goes up. That includes health care workers, people who live in dormitories, prison workers or inmates.

NCHN: Is mixing and matching vaccines safe? Is there a specific vaccine pairing that’s better or worse?

Wolfe: The question that was always out there was maybe the best defense here for COVID is to stimulate the immune system in a couple of different ways? This was documented both in international trials already, but domestically in the NIH trial, which was that whichever order of vaccines you give, the better responses appeared to be in the group who took the mRNA doses. 

So whilst it’s now allowed and safe and quite effective to really get any boost following any original course, it does appear that the best antibody responses are if you start with an mRNA dose and finish with an mRNA dose. If you are someone who took J&J because maybe you prefer a single jab, it’s very clearly better that your boost be an mRNA dose.

I appreciate the anxiety but I also think it’s worth knowing that there’s been no signal that there’s anything worse or different about the boosters. I’ve cared for a lot of people who’ve died for COVID, I haven’t cared for a single person who’s died because of problems with the vaccine.

NCHN: Probably people are worried if they have the J&J and Thanksgiving is coming up. Should those people be getting a booster?

Wolfe: Having… a J&J dose, I consider much more permissive to anyone just going up and requesting a booster because of that little difference that exists in effectiveness.

You’ll see the recommendations for a boost after a Pfizer or Moderna, you can wait six months, and we can reasonably expect to have great protection in those six months. Whereas what you see for J&J is they say, as soon as you’re two months out, go get another one.

The restrictions that existed on a booster for Pfizer or Moderna do not apply to J&J.

NCHN: And what about those holidays?

Wolfe: If you think back to last year, we had a really significant tee-off event by having this sequence of Halloween, Thanksgiving, the end of the college year, into Christmas and the New Year and rates skyrocketed. And why? Last year, we were all unvaccinated, but partly it was just the sheer number of congregating events going through the roof, and it was winter and we were all huddled inside huddled closer together. 

Many infectious disease specialists would feel that this year will not be as bad as last. Equally as many would say they expect the numbers to go back up again because we still have a large group of people who are unvaccinated. 

Probably more than last year, people want to get back to healthy Christmas parties and families they might have deferred from visiting last year. There’s gonna be greater incentive to hang out with people. I think that’s a great incentive to want to go ahead and get boosted. You are far enough ahead of time now, to get a booster that will meaningfully affect you in a good way before Thanksgiving. You can’t expect to get the jab in the arm today, and tomorrow to get great protection. That takes 10 to 14 days.

NCHN: For people who are considering getting a booster, how should they make that judgment call?

Wolfe:  At the end of the day, if they’re on the fence, they might as well get the booster. I really don’t see much of a downside. I think the next three or four weeks is a really good time to gain protection for the upcoming winter months. 

If you only got vaccinated two or three months ago, you can take it to the bank that your Pfizer vaccine or Moderna vaccine is really active still, and your chance of having any problem are so low that we don’t recommend those people get a booster. 

If you’re more than six months from an mRNA, those who are high risk or more than two months out from a J&J, I think it does make sense to get a booster.

shows a pair of gloved hands handling a syringe of COVID vaccine, you can read the name "Moderna" on the vial
Tia Belvin fills syringes of the Moderna COVID-19 vaccine for administration at a UNC Health mass vaccination clinic in Chapel Hill in January. Photo credit: Rose Hoban

NCHN: Is getting a booster just about antibodies, or is it more than that?

Wolfe: The greatest response seems to be how well you make antibodies. When you try and really study that very carefully, the reality is that people who get their antibodies through vaccination compared to those who get them through “natural infection,” unfortunately, the natural protection is not as strong. Those individuals were five times as likely to get breakthrough infections.

Natural infection clearly helps. But, the unfortunate reality is that natural immunity is very variable across people. And the people who had relatively simple infections the first go around develop the least robust immune response. The people who got the minor illness, unfortunately, sometimes fall into the trap of thinking it will be really simple, “I’ll be fine.” And they probably will be but that does not mean they’re not infectious to people.

I think once kids are vaccinated, you get that large chunk of those vaccinated, that’ll make a big difference for us, but they’re not going to be heavily vaccinated in time for Thanksgiving. It depends a lot on where you are in the country. So if you’re traveling to Massachusetts, your chance of being around unvaccinated people is actually really small, whereas if you are traveling to Florida, to the South, upper Midwest, there’s large counties in North Carolina, for example, that are less than 40 percent vaccinated. I do fear there’s going to be significant COVID spread.

NCHN: And what about the flu shot? Should we be getting that? Can you get a flu and booster shot together?

Wolfe: There are trials that show good safety for doing flu and COVID together. So that’s what I do in my clinic. That’s quite safe and equally efficacious. Our immune system deals with multiple things all the time.

This article first appeared on North Carolina Health News and is republished here under a Creative Commons license. North Carolina Health News is an independent, non-partisan, not-for-profit, statewide news organization dedicated to covering all things healthcare in North Carolina. Visit NCHN at

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