They could begin to emerge in the coming days following recommendations from the US Centers for Disease Control and Prevention (CDC), which will hold a meeting of its expert advisers on Thursday. Here’s what you need to know:
Who should get the updated booster?
Anyone 12 years and older who received the original two-dose vaccine and who is at least two months away from receiving a booster shot is eligible. Pfizer’s vaccine is approved for ages 12 and older, while Moderna is for ages 18 and older.
Government health officials say boosters are needed because vaccines help prevent serious illness and death, as immunity wanes over time. They also say young people could benefit as officials hope the new injectables can help prevent Covid, which can involve a range of debilitating symptoms rather than lingering for months.
Many experts say they don’t expect the updated vaccines to be game-changing and have urged public health officials not to exaggerate their benefits.
Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center and a consultant to the CDC, said the agency’s recommendations should provide information about who should get the shots.
What if I have recently received Covid or Booster?
While the FDA said updated vaccines should be given at least two months after a previous booster shot or infection, many vaccine experts have said the gap between doses is too short.
“It should have been at least four months, and I think a lot of immunologists would be happy if it was six years,” said John Moore, professor of microbiology and immunology at Weill Cornell Medical College in New York.
Boosting antibody levels restores a person to where they were after their most recent exposure to the virus through vaccination or infection, he said.
In fact, if antibody levels are relatively high when someone receives a new booster, they may interfere with the booster’s effect, he said.
What does the data say?
The FDA based its decision on data from human trials of so-called bivalent vaccines that covered the first version of the coronavirus and earlier variants, including the BA.1 Omicron variant that dominated last winter.
Pfizer and Moderna also provided data on BA.4/BA.5 boosters from laboratory and animal studies.
Because the vaccine is more compatible with the BA.5 subvariant of the virus that is still widely circulating, it will be more successful in preventing infection than vaccines that target only the original virus.
“It’s on the wish list, but we don’t know if it will be updated,” said Dr. Eric Topol, a genomics expert and director of the Scripps Research Translational Institute in La Jolla, California.
He said the improved injections will work against Omicron’s new subtype BA.4.6, which is on the rise in the US.
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