Pfizer booster spurs immune response to new Omicron subvariants

Ryan Dutton prepares shots of Pfizer's COVID-19 booster during a vaccine clinic in Townshend, Vt.
Pfizer’s updated boosters aren’t an exact match to the newest Omicron subvariants, but lab tests suggest they may offer some cross-protection, the company says.
(Kristopher Radder / Associated Press)

Pfizer said this week that its updated COVID-19 booster may offer some protection against newly emerging Omicron subvariants, even though it’s not an exact match to them.

Americans have been reluctant to get the updated boosters rolled out by Pfizer and rival Moderna, which were tweaked to target the BA.5 strain of Omicron that was dominant in the U.S. until recently. With relatives of BA.5 on the rise, many wonder how well the new boosters will hold up.

Pfizer and its partner BioNTech said Friday that their updated booster generated virus-fighting antibodies that can target four additional Omicron subtypes, including the particularly worrisome BQ.1.1.

The immune response wasn’t as strong against the newer subvariants as it is against BA.5. But adults 55 and older experienced a nearly nine-fold jump in antibodies against BQ.1.1 a month after receiving the updated booster, according to a study from the University of Texas Medical Branch in Galveston and the companies. That’s compared to a two-fold rise in people who got a booster of the original vaccine.

The preliminary data were released online and have not been vetted by independent experts.

It’s not the only hint that the updated boosters may broaden protection against the still-mutating coronavirus. Moderna recently announced early evidence that its updated booster induced antibodies capable of neutralizing BQ.1.1.

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It’s too soon to know how much real-world protection such antibody boosts provide, or how long they last. Antibodies are only one type of immune defense and naturally wane with time.

The BA.5 variant was responsible for an estimated 24% of new COVID-19 cases in the U.S. as of Nov. 12, according to the Centers for Disease Control and Prevention, but two new variants have been crowding out the once-dominant strain in recent weeks. BQ.1.1. now accounts for 24.2% of cases, up from 2% in early October, and close cousin BQ.1 accounts for 25.5%.

The original COVID-19 vaccines have offered strong protection against severe disease and death no matter the variant.


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That’s a good reason to stay up to date on boosters, Dr. Kathryn Stephenson of Beth Israel Deaconess Medical Center said this week, ahead of the release of Pfizer’s data.

“Any kind of boost really reduces your chances of getting very sick from COVID,” she said.

Updated boosters are available for anyone age 5 or older, but only about 35 million Americans have gotten one, according to the CDC. Nearly 30% of seniors, but only about 13% of all adults, are up to date with the newest booster.