WASHINGTON (Reuters) -The White House told U.S. states on Tuesday they can no longer carry over unordered doses of their weekly COVID-19 vaccine allocations and that unused doses will instead be shifted to states with greater demand, the Washington Post reported.

COVID-19 vaccines are currently allocated state by state based on population – a formula the Biden administration held to even as some states such as Michigan saw recent surges of the coronavirus.

But White House Coronavirus Task Force Coordinator Jeff Zients told the Washington Post in an interview that the change in allocation reflects the next phase in the White House’s efforts to inoculate the population.

“There is a need to add more flexibility to the current system,” he told the news outlet.

The shift also comes as new U.S. COVID-19 cases fell for the third week in a row. About 30.5% of the U.S. population, or about 101,407,318 people, have been fully vaccinated as of last week.

Representatives for the White House could not be immediately reached for comment on the report.

(Reporting by Susan Heavey; Editing by Tim Ahmann and Nick Macfie)