To Boost Again, and When? That Is the Question


a photo of an arm with multi-colored medical adhesive strips

Across the United States, 67% of the population has received their first series of COVID-19 vaccinations and 33% have also received a booster.

This varies quite a bit by age, with more than 92% of those older than 65 being vaccinated and a majority of that group having received at least one booster. 

Now, an Omicron-specific booster has been authorized by the FDA, the first redesign of the coronavirus vaccine since it became available in late 2020. These new boosters target Omicron subvariants, and the goal is for the redesign to help elevate antibody levels in a way that restores the protection conferred by the initial vaccines against symptomatic infection in many people. These new boosters are made by both Pfizer and Moderna. Pfizer’s is available for people as young as 12, and the Moderna booster is for those 18 and older. 

a portrait of Jodie Guest

Jodie Guest

Jodie Guest, professor and senior vice chair of the department of epidemiology at Emory’s Rollins School of Public Health, teamed up with Carlos del Rio, distinguished professor of medicine, epidemiology, and global health and executive associate dean of Emory School of Medicine at Grady Health System, to discuss the new boosters. Their conversation is part of an online video series hosted by Guest, who leads the Emory COVID-19 Outbreak Response Team, answering questions related to the COVID-19 pandemic. 

Q: What is different about these boosters? 

This vaccine is called a bivalent vaccine because it has two different antigens in it. It contains the original strain, like the previous vaccines, but it also contains a BA.4/BA.5 antigen. The idea is that it will give protection also against BA.4/ BA.5, which is the most common strain circulating right now. This new booster is approved for ages 12 and older; however, if you’re between 12 and 18, you will receive Pfizer because Moderna hasn’t been approved for that population yet. If you’re over 18, it doesn’t matter—you can take either Pfizer or Moderna. The boosters we had previously are no longer available. If you have not been vaccinated yet at all, you need to get your primary series with the original vaccines— could be Pfizer, could be Moderna, could be Johnson & Johnson, could be Novavax. You can get any of those vaccines and then you can get a booster with this bivalent vaccine. 

Q: Who needs to get this new bivalent booster?

Anyone over the age of 12 who has received their primary series of COVID-19 vaccine is eligible to get the new booster. A “big concern is that we don’t have a high percentage of the population boosted—in particular, people over 50, who are at high risk of severe disease and death,” says del Rio. “So we need to make an effort, clinically and in public health, to target the people that need to get boosted. When people over the age of 50 say, ‘Do I need to get boosted?’ I say, ‘Absolutely.’ For people over age 65, I say even more so, ‘Absolutely.’ But for people under 50, I say, ‘Yeah, get it if you want to, but it’s not really that important for that younger age group . . . . It’s going to help you some, but it’s not going to be a slam dunk.’ ” 

Q: When should individuals get this new booster? 

“We do have some modeling that suggests that there will be a fall wave that would peak around December 1, and so rolling out this new vaccine at this time is really meant to help control current infections and also protect against this future surge, which we should all want to do,” Guest says. Yet, both del Rio and Guest agree that if you got your last booster within the last four months, or you got infected within the last three months: wait. You don’t need to get it right away. In fact, there is [some evidence] that getting your booster within three months after an infection blunts the impact of the booster. Del Rio says, “If you got infected with Omicron in July, in August, last month? Wait until November. Now, if someone is in their late 60s, who has never had COVID that they know of, got their last booster in March? Absolutely, go and make your appointment and get the new booster right away.” 

Q: How can we be sure the new booster is safe? 

They changed the antigen, not the mechanism, for this new vaccine. Clinical trials aren’t necessary when you’re just making changes in the antigen. 

Q: Are we going to need new boosters routinely? “We should stop calling them boosters, because this is not really a booster, it’s a different vaccine. We don’t tell people that you’re going to get your flu booster, right? Every year we say ‘You’re going to get your flu vaccine.’ We need to get away from this terminology of boosters and say, ‘You’re getting your COVID vaccination.’ It may not be annual; it may be biannual. But getting away from the concept of a booster and into the concept of a regular vaccination, just like we do with the flu, I think that’s a good way to think about this going forward,” says del Rio. 

Q: If someone hasn’t gotten any of their initial series of vaccinations, can they start with this new bivalent vaccine? 

They need to have the original vaccines. “They need to go to A before they go to B. This is following your ABCs. We have the data that priming your immune system with the original vaccine is important,” says del Rio. “It’s not too late to start them,” says Guest. “We know that there’s a wide variability in uptake, particularly by ages, and there has not been a large uptake in our youngest children who are available to get these vaccines, even as school has started.” 

Q: People ask, “Should I be mixing and matching?” For example, if your original series was Moderna, should your booster be Pfizer? 

a portrait of Carlos Del Rio

Carlos Del Rio

“I tell people to get whatever is there and whatever is available,” says del Rio. “There’s no point in purposely mixing and matching. The mixing-and-matching studies that were done show that it’s safe, there’s no contraindication. But there’s really no additional benefits. Quite frankly, your immune system doesn’t really know the difference, and that’s why the Advisory Committee on Immunization Practices in their most recent recommendation did not say the names, they said, ‘We’re approving mRNA bivalent boosters.’ ” The only real difference will be if you’re between the ages of 12 and 18, and “that’s when you’re going to be getting Pfizer and not Moderna,” says Guest. “But the place that you go to get your vaccine will certainly be able to help walk you through that.” 

Q: Where is the new booster available? 

The government has done an incredible job getting these vaccines into pharmacies. The idea is that 90% or more of Americans are going to be five miles or less from a site where you can get a vaccine. So, if you go to and enter your zip code, it’s straightforward to find vaccine availability. 

Q: Can I receive a COVID-19 vaccine or booster at the same time as my flu vaccine? Or a monkeypox vaccine? 

The answer is yes. There’s no problem with combining them and it will not change the effectiveness of the vaccines. Del Rio says, “I always tell people, ‘Never miss an opportunity to vaccinate.’ The value of vaccines, whether it’s COVID vaccines or any other vaccines — it’s enormous.” 

Watch the Interview Here

In September, the CDC approved updated versions of the COVID-19 booster shots. Join Emory epidemiologists Dr. Jodie Guest and Dr. Carlos del Rio as they team up to answer questions about the new vaccines, including who is eligible and when to get your next shot.


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