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What We Know About New COVID Boosters as FDA Authorizes Updated Vaccine

Here's everything we know about the new boosters, including how they're different, what still needs to happen and when shots could begin

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New COVID-19 booster vaccines could begin in a matter of days after they were authorized by the Food and Drug Administration Wednesday, but more still needs to happen before shots can go into arms.

The move by the FDA tweaks the recipe of shots made by Pfizer and rival Moderna that already have saved millions of lives just ahead of the Labor Day holiday weekend. The hope is that the modified boosters will blunt yet another winter surge.

Here's everything we know about the new shots and when they could begin.

How Are the New Shots Different?

Until now, COVID-19 vaccines have targeted the original coronavirus strain, even as wildly different mutants emerged. The new U.S. boosters are combination, or “bivalent,” shots. They contain half that original vaccine recipe and half protection against the newest omicron versions, called BA.4 and BA.5, that are considered the most contagious yet.

The combination aims to increase cross-protection against multiple variants.

“It really provides the broadest opportunity for protection,” Pfizer vaccine chief Annaliesa Anderson told the AP.

Who Would Be Eligible?

The updated boosters are only for people who have already had their primary vaccinations, using the original vaccines. Doses made by Pfizer and its partner BioNTech are for anyone 12 and older while Moderna's updated shots are for adults — if it has been at least two months since their last primary vaccination or their latest booster. They're not to be used for initial vaccinations.

Still, the Centers for Disease Control and Prevention will need to make a recommendation on who should get the new booster dose.

What Still Needs to Happen and When Could Shots Begin?

There’s one more step before a fall booster campaign begins: The CDC must recommend who should get the additional shot. An influential CDC advisory panel will debate the evidence Thursday — including whether people at high risk from COVID-19 should go first.

The U.S. has purchased more than 170 million doses from the two companies. Pfizer said it could ship up to 15 million of those doses by the end of next week.

What If You Already Had a Booster?

The FDA authorization recommends waiting two months from your last booster for those who received one, before getting the new shot, but additional guidance is also expected from the CDC as they weigh a recommendation.

"They will weigh in on exact timeframe," Chicago Department of Public Health Commissioner Dr. Allison Arwady said Tuesday. "So I don't have answers for that just yet, but the bottom line is even if you didn't get a booster in the past, we are expecting that you will be able to get this booster."

How Well Will the New Shots Work?

Since July 2, the BA.5 omicron subvariant has been the dominant strain of COVID in the United States, and according to Chicago’s top doctor, that is a good thing for the updated vaccines.

Arwady said that the continued dominance of BA.5 has prevented another COVID variant from taking a foothold, and could mean that boosters will be even more effective in preventing breakthrough infections and serious illness.

“My concern was that we may see a new variant emerge before we got the new vaccine, and you’d be right back where you started,” she said. “If this pattern can hold, and we can quickly roll out this updated vaccine in September, and we see a lot of good uptake, it would, I think, have the potential to really help cut the risk of breakthrough infections, and have a significant impact on transmission.”

Marks said last week that once authorized, the tweaked boosters could help right away — while BA.5 infections still are too high — as well as hopefully blunt yet another winter surge.

Marks told the Associated Press that the new boosters could rev up the immune system to prevent not just serious illness but maybe milder infections, too, like the original vaccines did earlier in the pandemic, before super-contagious mutants emerged.

“The hope here is that by better matching things, not only will we get that benefit or even more, but we'll also have that last for a longer period of time,” he said.

But Dr. Paul Offit, a vaccine expert at the Children’s Hospital of Philadelphia and an FDA vaccine adviser, said the antibody jump from that earlier BA.1-tweaked candidate was “underwhelming.”

“What the administration is asking us to do is to accept this bivalent vaccine as significantly better” than another dose of today’s vaccine, he said. “It would be nice if there were data to support that.”

The original vaccines still offer strong protection against severe disease and death from COVID-19 for most generally healthy people, especially if they got that important first booster dose. It’s not clear just how much more benefit an updated booster will bring — beyond a temporary jump in antibodies capable of fending off an omicron infection.

One reason: The FDA cleared the modifications ahead of studies in people, a step toward eventually handling COVID-19 vaccine updates more like yearly flu shots.

First, FDA checked human studies of earlier Pfizer and Moderna attempts to update their vaccines — shots matching the omicron strain that struck last winter. That recipe change was safe, and substantially boosted antibodies targeting the earlier variant — better than another dose of the original vaccine — while adding a little protection against today's genetically distinct BA.4 and BA.5 omicron versions.

But FDA ordered the companies to brew even more up-to-date doses that target those newest omicron mutants instead, sparking a race to roll out shots in less than three months. Rather than waiting a few more months for additional human studies of that recipe tweak, Marks said animal tests showed the latest update spurs “a very good immune response.”

The hope, he said, is that a vaccine matched to currently spreading variants might do a better job fighting infection, not just serious illness, at least for a while.

"This is actually how we do updated flu vaccines every year," Arwady said. "So it's nothing different from that. So, what I would say is that this exact updated vaccine did not have the full scope of, like, the extended human trial, like an earlier one would have, but that's not a concern from a safety or efficacy standpoint because it was done with the earlier versions and using the same technology."

When is the Best Time to Get Your COVID Booster Shot?

How long to wait after your last vaccine dose or an infection is a critical decision, immunologists agree. That’s because if you still have a lot of antibodies in your bloodstream, they’ll counteract the brand new antibodies that the vaccine dose is supposed to produce.

The FDA authorization suggests a two-month waiting period from your last vaccination, but the CDC also will weigh in after after considering how many doses will be available in early September versus later in the fall.

How Were the Shots Tested?

Pfizer and Moderna both studied an earlier tweak to their vaccines that targets the original omicron, called BA.1, that hit last winter, as well as even earlier variants.

To evaluate the combo shots, FDA is using data from human testing of the BA.1-tweaked doses plus mice tests of the BA.5-targeted version that Marks said show “a very good immune response."

Human data on the newest tweak will come later in the year, to help assess the value of modified shots — especially whether they offer cross-protection if a new mutant comes along, Marks said. Moderna has started a clinical trial of its BA.5 combo shot; Pfizer and its partner BioNTech expect to open a similar study soon.

"There will certainly be all of the monitoring and I'm actually really interested to see the efficacy of this for BA.4 and [BA.5] in particular - I expect it will be good," Arwady said. "And there are, if you look at all of the advisory groups, the experts - there's not any safety concerns related to the release of this. It's more a question of the efficacy."

Can You Mix-and-Match?

Additional guidance on this is expected along with final approval and recommendation from federal officials, but Chicago's top doctor believes people will be encouraged to get whichever booster they can.

"I think it's fine, honestly, to get either of them at this point," Arwady said. "And I do think we're getting some preliminary information. For example, how much vaccine we'll be receiving in Chicago? It looks like, and I know that the federal government has purchased more... Pfizer boosters than Moderna and so it may be a little easier to find Pfizer. That said, we know Pfizer was first, we know Pfizer is the one that the especially the 12- to 17-year-olds can get. So it may be a little easier to find a Pfizer vaccine than a Moderna vaccine, but I would just honestly encourage you to get whichever one whichever one is available."

NBC Chicago/Associated Press
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