U.S. Not Likely to Allow Half-Doses of Moderna’s Vaccine for Younger Patients

Late Monday, the FDA’s two top officials hinted that the agency is unlikely to adopt the Trump administration’s idea of giving two half doses of Moderna’s COVID-19 vaccine to patients aged 18 to 55 in order to double the number of vaccinations being administered, as suggested by Operation Warp Speed’s chief adviser Moncef Slaoui.

“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,” said FDA Commissioner Stephen Hahn and Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, in a joint statement.

“We have committed time and time again to make decisions based on data and science. Until vaccine manufacturers have data and science supporting a change, we continue to strongly recommend that healthcare providers follow the FDA-authorized dosing schedule for each COVID-19 vaccine,” the statement said.

Addressing questions about the federal government’s slower-than-anticipated vaccine roll-out, Slaoui said that while the FDA would ultimately need to sign off on it, the data support the half-dose regimen, and the government is in talks with both the agency and Moderna about the shift.

“We know that for the Moderna vaccine, giving half the dose to people between the age 18 and 55 … which means exactly achieving the objective of immunizing double the number of people with the doses we have, we know it induces identical immune response to the 100-microgram dose,” Slaoui said.

Despite the administration’s ambitious goals of having 20 million people vaccinated by the end of 2020, only 4.2 million had received their first shots of either the Moderna or Pfizer/BioNTech vaccines as of Saturday morning, according to Centers for Disease Control and Prevention (CDC) data. According to CDC stats, approximately 13 million doses of the two-dose vaccines have been distributed to states so far.

Slaoui argued the proposed half-dose plan is more scientifically responsible than the UK’s strategy, which involves vaccinating as many people in priority groups as possible with initial vaccine doses even if it means delaying second shots. The U.S. currently employs a strategy of holding back shots to ensure vaccinated patients will receive their second doses.

“I think it’s not reasonable, when vaccines have been developed with two doses given 21 days apart or 28 days apart, and when we have the data on their safety and efficacy after two doses,” he said. “We have no data after one dose [on what happens] if we leave people a month, two months, three months, with maybe incomplete immunity, waning immunity, maybe even the wrong kind of immune response induced.”

Slaoui didn’t specify when a decision would be made on the half-dose strategy but the FDA will reportedly meeting this week to discuss it.

In an interview Monday, former FDA chief Scott Gottlieb voiced support for the alternative measure as long as the data support it.

“They may move to that,” he said. “If you can cut the Moderna [doses] in half for the younger cohort, that’s significantly more doses than the 200 million we talk about that’s going to be available in the first half of the year.”

Moderna announced yesterday that it estimates producing a global supply of 600 million vaccine doses in 2021 and said that it is continuing to work toward producing 1 billion doses this year.

The drugmaker expects to make 200 million doses available in the U.S. by the end of the second quarter per its recently expanded agreement with the government (DID, Dec. 28, 2020). The company claimed it has supplied approximately 18 million doses to the U.S. so far.

Meanwhile, although the European Medicines Agency’s advisory committee met Monday ahead of schedule to discuss conditional marketing authorization for Moderna’s vaccine, the agency said that the committee will still meet tomorrow as planned, dashing hopes of an earlier authorization. — James Miessler