Earlier this month, the CDC endorsed updated versions of the mRNA COVID-19 booster shots. These bivalent boosters are designed to target the most recent — and more transmissible — Omicron subvariants, BA.4 and BA.5.
In response to the new recommendation, Jodie Guest, PhD, professor and senior vice chair of the department of epidemiology at Emory’s Rollins School of Public Health, teamed up with Carlos del Rio, MD, distinguished professor of medicine, epidemiology and global health and executive associate dean of Emory University School of Medicine at Grady Health System, to answer questions about the new shots. They discuss who is eligible for the updated boosters, the safety and efficacy of the vaccines and how this booster differs from previous COVID-19 shots.
Q: These vaccines are ‘bivalent.’ What does that mean?
A: The new vaccines are bivalent, meaning that they contain two antigens: both from the original strain of coronavirus and from the Omicron BA.4 and BA.5 subvariants. The vaccines were re-tooled in an effort to boost protection against Omicron, which has become the dominant strain.
“The goal is for the redesign to help elevate antibody levels in a way that restores the protection inferred by the initial vaccines against symptomatic infection in many people,” says Guest.
“This has two different antigens in it, and the idea is that will give protection against BA.4 and BA.5, which is the most common strain circulating right now,” adds del Rio. “To remind people, for example, the flu vaccines we typically take are trivalent, because they cover three different flu strains.”
The process of updating the mRNA vaccines — made by Pfizer and Moderna — is “pretty straightforward,” del Rio says. “Basically, you're changing your cassette tape. So, you just take out one and you put in another one — you’re just changing the protein.”
Q: Are the new boosters safe?
A: The new boosters are safe. They were authorized by the FDA and CDC following the same process used to approve updated flu vaccines each year, del Rio says.
“You don’t really need data from clinical trials once you’re just making changes in the antigen,” he says. “Let me give you an example: I have Goodyear tires on my car, and I get a flat tire and the Goodyear tire is not available, but the guy at the store says, ‘Well, we do have a Michelin tire,’ and I say, ‘No, I can't have a Michelin tire, because my car is not going to be safe.’ It’s a different brand, but if it’s the same size tire, the same type of tire — it’s going to work just as well. You don’t do testing to see if that’s a safe tire. That’s what’s happening here. You’re just changing the antigen, but you’re getting the same mechanism.”
Q: Who is eligible for the new boosters? When is best to get the next shot?
A: “These new boosters are made both by Pfizer and Moderna. Pfizer’s is available for people as young as the age of 12, and the Moderna booster is for those 18 and older,” Guest says.
Adults may receive an updated booster from either Pfizer or Moderna at least two months after completing their primary vaccination series or after receiving their last booster. At this time, children as young as age 12 may only receive the Pfizer booster at least two months after their second dose or last booster.
“I tell people if you got your last booster within the last four months or if you got infected within the last three months, wait [to get your updated booster],” del Rio says. “You don’t need to get it right away. There’s a recent article in pre-print from Dr. Fauci’s laboratory suggesting that after an infection, getting your booster within three months — simply, the B cells are not ready. It blunts the impact of the booster.”
Del Rio recommends that individuals who have not had COVID-19 in the past three months or who are four to six months away from their last COVID-19 vaccine go ahead and receive the updated booster — particularly those over age 50, and especially those over age 65.
“Go and make your appointment and get it right away, because you’ll probably get the benefit of it,” he says, adding that the booster is designed to decrease one’s chances of developing severe disease and dying.
Q: Is it still safe mix and match COVID-19 vaccines?
A: Studies have shown that it is safe to mix and match COVID-19 vaccines from different manufacturers. For example, it is safe to receive a Pfizer booster shot even if you received Moderna shots for your primary vaccination series.
While it is safe to mix and match, there is no significant benefit to doing so intentionally, del Rio notes.
“If you’re over eighteen, I tell people to get whatever is available. There’s no point to purposely mixing and matching,” del Rio says. “Quite frankly, your immune system doesn’t really know the difference, and that’s why in their most recent recommendation the ACIP did not say the [brand] names; they said, ‘We’re approving mRNA bivalent boosters.’”
Q: Can you start a primary vaccination series with the updated booster?
A: At this time, only the original COVID-19 vaccines are available for the primary vaccination series. There are not yet data to indicate whether starting a vaccination series with the bivalent vaccine is effective, but, del Rio says, “we do have the data that priming your immune system with the original vaccine is going to be important.”
Q: Will there be another surge of COVID-19 this fall and winter?
A: “We do have some modeling that suggests that there will be a fall wave that would peak around Dec. 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.
Q: Can you get the updated booster at the same time as a flu shot?
A: “Yes, there is no problem with you doing that. Some people don’t like to do it because one of the major side effects of both vaccines is soreness in the arm,” del Rio says. “At the end of the day, make it what is convenient. If you want to space them out, it’s fine, but you can certainly take them together.”
Q: Can you get the updated booster at the same time as a monkeypox vaccine?
A: “Again, the answer is yes,” del Rio says. “I always tell people, ‘Never miss an opportunity to vaccinate.’”