U.S. offifficials consider half-doses of vaccine

A top offifficial of Operation Warp Speed floated a new ideaSundayforstretchingthe limited number of COVID-19 vaccine doses in the United States: halving the dose of each shot of Moderna’s vaccine to potentially double the number of people who could receive it.

Data fromModerna’s clinicaltrialsdemonstratedpeople betweenthe agesof 18 and55 who received two 50-microgramdoses showedan“identicalimmuneresponse” tothe standard of two 100-microgramdoses, said the offifficial, Dr. Moncef Slaoui.

Slaoui said that Operation Warp Speed was in discussions withthe FoodandDrug Administrationandthepharmaceutical company Moderna over implementing the half-dose regimen.

Eachvaccinewould still be delivered in two, on-schedule doses four weeks apart, Slaoui said in an interview with “CBS’ Face the Nation.” He said it would be up to the FDA to decide whether to move forwardwith the plan.

Ray Jordan, a spokesperson for Moderna, did not comment on Slaoui’s proposal, but noted thatModerna’s late-stage clinical trials focused on a regimen of two doses of 100 micrograms of vaccine apiece, spaced four weeks apart. This was the same schedule and dosing that earned the vaccine its emergency green light from the Food andDrugAdministration last month.

Slaoui was asked whether the United States would followBritain’s lead onanother tactic for getting shots to more people: delaying second doses of newly authorized vaccines to immunize a larger swath of the population. There is little or no data on dose delays, Slaoui said, but “injecting half the volume” might constitute “a more responsible approach that will be based on facts and data to immunize more people.”

Natalie Dean, a biostatistician at the University of Florida, agreed that there might be more data to support a vaccine strategy that relied on half-doses rather than delayed doses.

“There is a path forward if you canshowthat two lower doses yield a similarimmune response,” Dean said.

As caseloads continue to surge upward around the globe, and concernsmount over a new and potentially more transmissible variant of the coronavirus, “everyone is looking for solutions rightnow, becausethereisan urgentneedformoredoses,” Dean added.