the initial dose, the agency noted the data is limited, saying a key test used by the company was likely not sensitive enough adding the fda didn't have enough time to independently review much of the raw data from the trial ahead of an advisory panel meeting this friday it is not clear whether these concerns would be enough to delay emergency use authorization. >> we have the vaccine supply, and we will be ready to hit the ground running as soon as any additional boosters are authorized >> reporter: and now a new highly anticipated study by the nih shows mixing and matching vaccine boosters is safe and effective. the study added j&j covid vaccine recipients are better off getting pfizer or moderna boosters the fda advisory panel will review it on friday. meanwhile, the white house is also telling governors to start preparing to vaccinate children as young as five by early next month. in anticipation of clearance of pfizer's vaccine for that age group in the coming weeks.