Vaccines from Pfizer and Moderna are meant to be administered in two doses given three or four weeks apart, respectively, but the CDC updates its guidance, saying the second dose can be given up to six weeks after the initial dose. 'In exceptional situations in which the first-dose vaccine product cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses.' The seven-day rolling average for new COVID-19 vaccines being administered is already at 940,000 a day It came as Biden signed a new executive order on Thursday to speed up vaccine delivery and doubled-down on his plan to hand out one million doses per day.