Bivalent boosters protect against the super-infectious new variant XBB.1.5, new data finds

On Wednesday, the Centers for Disease Control and Prevention (CDC) released early data on the effectiveness of the updated COVID-19 boosters and how they're faring against the most common omicron subvariants, known as XBB and XBB.1.5. 

Fortunately – given that America is in the middle of the winter COVID season — the news is hopeful.

In adults up to age 49, both boosters from Pfizer-BioNTech and Moderna were nearly 50 percent effective against symptomatic infections from both BA.5-related infections and XBB/XBB.1.5-related infections. However, for those 65 and older, effectiveness dropped to 37 percent against BA.5 and 43 percent against XBB/XBB.1.5.

The 37-to-50 percent range might not seem that high. But, in the grand scheme, these numbers are comparable to the standard range of flu vaccine effectiveness.

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist.

The report is based on COVID-19 test results of more than 29,100 adults with COVID symptoms who were tested at pharmacies nationwide between Dec. 1 through Jan. 13. As Salon previously reported, subvariant XBB.1.5 has been rapidly increasing in spread across the country and exhibiting disconcerting immune-evasive properties. Some hospitals have noted that they've seen a surge in cases, and some worry that the winter could be similar to last winter's COVID-19 outbreak. As of January 21, XBB.1.5 is responsible for about 1 in 2 new COVID-19 cases. 

"XBB is a different ballgame," Dr. Rajendram Rajnarayanan, an assistant dean of research and associate professor at the New York Institute of Technology campus in Jonesboro, Arkansas, previously explained to Salon. "With a recombinant, you get mutations that makes it more evasive. And as we expected, [XBB.1.5] changed one small mutation, a V changed to a P at the 486 position. And that's it. All of a sudden, it binds to the host receptor better than most variants that we know so far."

Dr. Brendan Jackson, the head of the CDC's COVID response, said in a call with reporters this week that the CDC's data was "quite reassuring." "These updated vaccines are protecting people against the latest COVID-19 variants,"Jackson said.

Unfortunately, not many people have received the latest and greatest booster; only about 15 percent of Americans have received a bivalent booster, according to CDC data. As Dr. Jenna Clark, a Senior Behavioral Researcher at Duke University's Center for Advanced Hindsight, previously wrote for Salon, the lack of people getting their bivalent boosters isn't necessarily a consequence of vaccine hesitancy. 

"The majority of people say the bivalent booster is as safe and effective as the original COVID-19 vaccine – if not more – and 70% of those already vaccinated against COVID-19 intend to get a booster in the next year," Clark explained. "But there's a big gap between intending to do something and actually getting around to it — and that is where the problem lies."

Experts hope the CDC's new data might motivate people to get these boosters.

"With this data, we see there is a benefit that might convince some people to sign up and get a bivalent booster," Dr. Peter Hotez, co-director of the Center for Vaccine Development at Texas Children's Hospital, told NBC News.