An Omicron booster?
Moderna released preliminary results today on an updated coronavirus vaccine targeting the Omicron variant, calling it “our lead candidate” to serve as a U.S. booster shot in the fall.
The firm tested a booster dose combining the original vaccine with one targeted specifically against Omicron. They found that the combination produced 1.75 times the level of neutralizing antibodies against Omicron as the existing vaccine alone.
But Omicron has been spawning subvariants for months, and some vaccine experts say what matters now is how well a new booster formulation would protect against the latest subvariants — BA.4 and BA.5, which now account for 13 percent of new cases in the U.S. — not Omicron itself. By some estimates, within a month they could outcompete the now-dominant Omicron subvariants BA.2 and BA.2.12.1.
The problem with targeting the newest versions of the virus is that Moderna and Pfizer do not have enough time to run more human clinical trials and still manufacture shots before the fall, when the Biden administration is hoping to be able to offer an updated vaccine for a potential winter surge. That might force regulators to choose updated vaccines based on data from laboratory tests and trials involving mice or other animals.