(CNN) The chief scientific adviser for Operation Warp Speed explained Sunday that an unpredicted "two-day lag period" is the reason why many states have not received the number of vaccines promised. Slaoui's comments on Sunday about the two-day lag come a day after Gen. Gustave Perna , the chief operating officer of Operation Warp Speed, apologized for miscommunicating the number of vaccine shipments to states. JB Pritzker said on Wednesday that he is expecting the reduction in vaccine doses "will likely cut our state's projected Pfizer shipments this month by roughly half." On Thursday, he tweeted that the state's vaccine allocation will be cut by 40% next week, and that "no explanation was given." In a tweet on Saturday , he explained that the "FDA is not requiring lot release for #COVID19 vaccine under EUA.

Source: CNN December 20, 2020 18:21 UTC