Update (January 5): On Monday evening, the FDA stated that dosing in the US will occur as planned, based on available data regarding efficacy, saying: “We know that some of these discussions about changing the dosing schedule or dose are based on a belief that changing the dose or dosing schedule can help get more vaccine to the public faster. However, making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health.”

Officials involved with the United States’s Operation Warp Speed—the program tasked with expediting the creation of a vaccine for COVID-19—are discussing the merits of rationing the Moderna vaccine for adults aged 18–55, as is being discussed in the United Kingdom. This would be accomplished either by giving half doses of the first shot or delaying the immunization’s second shot, Moncef Slaoui, the head of OWS, tells CBS News’s “Face the Nation.” Ultimately, the Food and Drug Administration will determine if the vaccines can be given on a different schedule, and a decision has not yet been made.

Originally, OWS anticipated that 20 million vaccine doses would have been distributed by the end of 2020. As of January 2, the Centers for Disease Control and Prevention reports that 13 million doses have gone out, and 4.23 million people in the US have received at least one dose, primarily frontline healthcare workers and nursing home residents so far. Going off-schedule for lower-risk adults would allow twice as many people to receive their first shot, Slaoui says. The vaccine’s urgency has become more pronounced as a more contagious strain of SARS-CoV-2 that originated in the UK has now been found in the US.

If reducing the volume of the first dose is approved by the FDA, the rationing would only affect the vaccine made by Moderna, Slaoui explains, which he claims would still provide the same protection as a full dose. Officials from Moderna have not yet verified if that is the case. Germany is also deliberating holding off on the second shot to spread around more initial doses, while Denmark has already approved the measure, Reuters reports.

Officials from Pfizer and BioNTech released a joint statement last week in response to the UK’s desire to hold off on the second dose from the initial plan of 21 days to as long as 12 weeks after the first. “The safety and efficacy of the vaccine has not been evaluated on different dosing schedules as the majority of trial participants received the second dose within the window specified in the study design,” the statement reads, according to Reuters.

Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, along with other medical experts around the globe, say they disagree that rationing would be effective, The New York Times reports. Fauci says that the US will not be following the UK’s lead to delay the second dose, should the British government decide to do that. Still, it will be down to the FDA to decide if altered dosing will be permitted.

Speaking on CNN, Leana Wen, the former health commissioner of Baltimore, agrees with Fauci’s take. “I understand the desire to stretch out the doses that we have and to say, ‘Hey, if one dose can offer some partial protection, why not give it to as many people as we can?’ The problem, though, is that is not how the studies were conducted.”