[Donger]

The US Food and Drug Administration will meet this week to consider giving half-doses of Moderna’s Covid-19 vaccine to people aged 18 to 55.

The move could make the vaccine available to twice as many people in this age group, according to Moncef Slaoui, chief scientific adviser of Operation Warp Speed, the US government's vaccine program.

Slaoui told CNN Chief Medical Correspondent Dr. Sanjay Gupta that the decision to cut the current 100-microgram dose in half, with another half-dose 28 days later, ultimately rests in the hands of the FDA.

Earlier data showed that binding and neutralizing antibody responses were similar among participants under 55 who received either 100-microgram or 50-microgram doses, Slaoui said. While an FDA briefing document last month also references these “comparable” immune responses from Moderna’s phase 2 study, the full data have not yet been published.

Slaoui said he’s “not sure it holds for Pfizer,” whose dose contains 30 micrograms. But that’s a conversation that has yet to happen, he added.

CNN has reached out to Moderna and Pfizer for comment. The US government previously secured 200 million doses each of Moderna’s and Pfizer’s vaccines.