A new COVID-19 booster shot targeting the highly transmissible omicron strain of COVID-19 is now available for people aged 12 and older, following a recent authorization from the U.S. Food and Drug Administration.

Daniel Kuritzkes, MD, chief of the Division of Infectious Diseases, spoke with Brigham Bulletin to address common questions about the new booster and flu shots.

Let’s start with the basics. What is different about this updated booster?

Daniel Kuritzkes

DK: The new COVID boosters are what we call a bivalent booster. Instead of having just one of the COVID variants represented in the vaccine, it includes two variants. So, in addition to having the original strain — often referred to as the Wuhan strain — the booster also includes the BA.5 subvariant of omicron. That’s important because it’s the strain causing the most infections today.

The concept of having multiple strains, or variants, represented in an individual vaccine is not new. The flu vaccine is a great example of this. For years, we used to get a trivalent, inactivated flu vaccine. Now, it’s standard to use a quadrivalent vaccine, which means there are four different strains of flu represented in the vaccine. Similarly, the polio vaccine had been a trivalent vaccine and is now a multivalent vaccine.

What do we know about how effective this booster is against the newer strains of COVID-19?

DK: We know these vaccines are safe and will generate the desired antibody response, which is what we believe is protective. The bivalent vaccine induces better antibody levels against omicron, including BA.5, than the original vaccines — all of which are based on the ancestral strain, which is quite distantly related to omicron. While we don’t have clinical trials data demonstrating just how effective the vaccine is against preventing infection, that is not unusual. We typically rely on so-called surrogate markers, or laboratory markers, of protection to move forward from one type of vaccine to another. Similarly, the flu vaccine is updated annually, and, clearly, we’re not doing clinical trials every year to demonstrate the efficacy of each season’s flu vaccine.

If you recently had COVID, would you still benefit from a booster? If so, when should you get it?

DK: Yes. We know that people who received the original vaccine series, had COVID and then got a booster had very strong protection. Even though the original vaccine — which remains the vaccine approved for primary vaccination — is not as protective against infection or symptoms of the current strains in circulation, it is still extraordinarily protective against severe disease, hospitalization or potentially dying of COVID.

The hope with the bivalent booster is that we gain a bit of an edge and perhaps return to better prevention of symptomatic infection, although that remains unproven. We’ll know in a few months just how successful it is.

In terms of timing, it’s recommended that people wait to get boosted until about three months after recovering from an episode of COVID, and at least two months since receiving their last booster or completing their primary vaccination series.

Does your booster need to be from the same manufacturer as your original vaccine?

DK: No, it doesn’t matter which one you had originally. You can get boosted with the Moderna or the Pfizer vaccine — which are the only ones authorized as boosters — regardless of which vaccine you had initially. My advice would be to find the place most convenient for you to get boosted and whichever booster they’re offering, that’s the one I would take.

With flu season soon upon us, can you get your flu shot and COVID booster together? Are there any concerns with, or benefits to, getting both at the same time?

DK: There are no concerns, other than potentially having a sore arm from each vaccine. I think it’s probably far more convenient for most people to go once to get both vaccinations.

It’s extraordinarily important for people to get their flu vaccine this season. It’s been a couple of years since we’ve seen much flu activity, but we already have clues from Australia about what to expect this flu season because they’re currently coming out of their winter. Now that very few places require masking or emphasize social distancing, they saw a lot more flu activity this season than in recent years.

It’s expected that we, too, will see a significant flu season here in the Northern hemisphere. And because people haven’t seen flu in a few years, immunity may have waned if they weren’t regularly vaccinated, so it’s important for people to do that this season. If you have symptoms, you should also get tested for both, since you can’t really tell flu apart from COVID based on symptoms alone. And if you do have symptoms of either respiratory illness, stay home until you’re symptom-free, so you don’t spread it to your co-workers, friends and other people in public spaces.