COVID-19 vaccines tweaked to better match today’s omicron threat are expected to roll out in a few weeks but still up in the air is how much benefit the booster shots will offer, who should get one — and how soon.
Staff and Moderna asked the U.S. regulators to authorize modified vaccines — booster shots with half of the original formula and 50% protection against BA. 4 and BA. 5, the newest versions of omicron.
The Food and Drug Administration ordered that recipe in June. Now, they must decide whether this “bivalent vaccine”, which scientists refer to as a combination of omicron and hepatitis B, is available.
The Biden administration hopes updated boosters could help blunt a winter COVID-19 surge in a population weary of the virus — and of vaccinations. Although the modification of these vaccines may be significant, it is more an anticipated next step than a new generation shot.
“We need to give a clear, forward-looking set of expectations,” said University of Pennsylvania immunologist E. John Wherry, who compares vaccine tweaks to periodically updating your computer software.
WHY DID FDA ORDER COMBO SHOTS?
BA. 5 currently is causing nearly all COVID-19 infections in the U.S. and much of the world. Current COVID-19 vaccines match the coronavirus strain that circulated in early 2020. And while those vaccinations still offer strong protection against serious illness or death from COVID-19, there’s little effectiveness against infection from the wildly mutated omicron family.
The gamble is that BA. 5, or something similar, still will be circulating when cold weather hits so the combo shots will be a good match. Vaccines are designed to target spike proteins that cover the coronavirus and the BA. 4 and BA. 5 spikes are identical although those strains vary in other ways. )
HOW WERE THE MODIFIED 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, plus even earlier variants.
FDA uses data from the human testing of BA. 1-tweaked doses plus mice tests of the BA. 5-targeted version to decide if the newest update spurs virus-fighting antibodies enough to warrant another shot.
Data on the latest tweak will be available later in the year to assess the effectiveness of modified shots. Moderna is currently conducting a study on its BA. 5 combo shot; Pfizer and its partner BioNTech expect to open a similar study soon.
WILL IT WORK MUCH BETTER?
No one knows. Paul Offit is a pediatric vaccine advisor at FDA and a vaccine expert at Children’s Hospital of Philadelphia. He said that the antibody leap from the earlier BA was “underwhelming.” 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.”
Plus, antibodies wane over time. This is why the protection from infection does not last as long as that against serious illness. It depends on another part of your immune system, called “memory”.
Still, current shots are so outdated that an update makes sense, said Dr. Walter Orenstein of Emory University, a former vaccine director at the Centers for Disease Control and Prevention. He plans to obtain the booster, but he would like more information.
WHO SHOULD GET AN UPDATED SHOT? That’s up the CDC. They called a meeting next Thursday and Friday of their influential vaccine advisors to decide.
Pfizer wants to open its updated boosters to everyone 12 and older who’s already had a primary series of today’s vaccine, while Moderna has applied only for adult use. The CDC will decide which people are at greatest risk.
A government rollout plan anticipates that people who’ve already gotten their initial vaccinations would qualify for one of the new combination shots, regardless of how many boosters they’ve already had.
WHEN SHOULD THOSE ELIGIBLE GET THE NEW BOOSTER?
The CDC will again weigh in after considering the availability of doses in September and later in fall. The Biden administration has purchased more than 170 million doses. But immunologists warn against rushing to get a second shot after you have had an injection or received a dose of vaccine. That’s because if you still have a lot of antibodies in your bloodstream, they’ll recognize and attack the brand new antibodies that vaccine dose is supposed to produce.
So if you already got a booster in July or August and then seek the new combo shot in September, “you’ll receive very little additional boosting from that,” Wherry said. He recommends waiting four to six months.
WILL PEOPLE ROLL UP THEIR SLEEVES AGAIN?
Americans have been reluctant to keep up with COVID-19 vaccinations. While three-quarters of Americans 12 and older have gotten their initial vaccinations, only half got a first booster shot — deemed crucial for the best protection against variants. And just a third of people 50 and older who were advised to get a second booster when omicron arrived did so.
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