Moderna Begins Testing Booster Shot Aimed at Omicron

Moderna Inc. announced Wednesday that it has launched a trial that will study the power of a redesigned booster shot -- one that homes in on the highly contagious omicron variant.

In announcing its trial, Moderna also explained why the newly formulated shot is needed: After a single dose of the current booster, the level of omicron-fighting antibodies rose 20 times higher than their peak before the shot, the company said. But those antibody levels had fallen more than sixfold six months later, though they were still detected in all of the booster recipients in the study.

"We are reassured by the antibody persistence against omicron at six months after the currently authorized 50 µg booster of mRNA-1273. Nonetheless, given the long-term threat demonstrated by omicron's immune escape, we are advancing our omicron-specific variant vaccine booster candidate," Moderna CEO Stéphane Bancel said in a company statement.

Although omicron can evade the antibodies elicited by authorized vaccines, making breakthrough infections more common, the vaccines still provide strong protection against hospitalization and death, several studies have already shown.

The new Moderna study will focus on a single omicron-specific booster dose in about 600 adults, broken into two groups: those who have received two doses of the current Moderna vaccine and those who have received two doses plus a booster. The company did not say when results could be expected.