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

The news comes just one day after Pfizer announced that it has started testing its own Omicron-specific shot.

In announcing its trial, Moderna also explained why the newly formulated shot is needed: A small lab study published Wednesday in the New England Journal of Medicine suggests the protection that Moderna’s authorized booster shot provides against Omicron fades in six months’ time.

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.

Moderna’s new 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 Moderna’s current vaccine, and those have received two doses plus a booster.

The company did not say when results could be expected.

Pfizer, which plans to enroll as many as 1,420 people in its study, said it expects to have results in the first half of this year.

Both Omicron-specific booster shots are being developed as the Omicron variant establishes its dominance in this country: The latest data from the U.S. Centers of Disease Control and Prevention show that 99.9% of U.S. COVID cases are now driven by the highly transmissible variant.

More information

Visit the U.S. Food and Drug Administration for more on COVID vaccines.

Source: HealthDay