New COVID-19 shots targeting omicron subvariant XBB.1.5 are slated to be ready in September. That strain only accounts for about 10 percent of U.S. cases, though experts say other circulating strains are similar enough to XBB.1.5 that the new shots should still be effective.
XBB.1.5 accounted for 10.3 percent of cases for the week ending Aug. 5, according to the CDC's latest variant proportion estimates. Meanwhile, EG.5 and XBB.1.16 collectively account for nearly 33 percent of cases. In June, when an FDA committee advised vaccine manufacturers to update shots to target XBB.1.5 ahead of a fall vaccination campaign, it was the dominant variant.
The top circulating strains today are still close relatives, so experts don't anticipate the new shot's efficacy to be affected much. In an Aug. 6 tweet, Eric Topol, MD, founder and director of the Scripps Research Translational Institute in La Jolla, Calif., noted the EG.5 is "gaining steam in the U.S. and many places globally," and shared a visual of XBB.1.15's spike protein that indicates it only has a few additional mutations relative to EG.5.
"The new COVID boosters, directed vs. XBB.1.5, are closely aligned, should be [very] effective vs. severe COVID, and are overdue," he said in the tweet.
Raj Rajnarayanan, assistant dean of research and associate professor in the department of basic sciences at the New York Institute of Technology College of Osteopathic Medicine at Arkansas State University in Jonesboro, agreed. He also runs a sequencing dashboard that tracks variant prevalence across the globe.
"New COVID Booster (XBB.1.5) is only a few spike mutations away from the top circulating SARS-Co-V2 lineage and should be effective in preventing severe COVID and hospitalizations, especially in senior and vulnerable populations," he said in a tweet.
Pfizer expects the FDA to authorize its updated shots by the end of the month, the company's CEO told investors during a recent call, NBC News reported.