Municipalities around Japan have begun preparing to inoculate millions of children age 12 to 17 after the health ministry signaled that the age restriction for COVID-19 booster shots would likely be lowered below 18 years old starting next month.

Vaccines from Pfizer-BioNTech and Moderna have been authorized as a third dose for people age 18 and over, but the government plans to authorize only the former shot for the younger recipients, and only after at least six months pass after receiving the initial two doses. The health ministry has advised municipalities to set aside enough doses for those under 18, but given the popularity of Pfizer shots among adults, some cities fear a potential supply crunch. As a result, some of these cities have given up on expanding reservation slots for the Pfizer booster for people age 18 and above.

“There is a lot of confusion in the field right now about what to do about additional vaccinations for children,” Shinji Hirai, governor of Tottori Prefecture and president of the National Governors’ Association, said to health minister Shigeyuki Goto during an online meeting on Monday.