The slow COVID-19 booster rollout in Japan is expected to accelerate in February, its third month, after the first two months ended with less than 4% of all residents in the country having received their third shot — less than a third of the government's target.

The campaign has been slowed by initial plans to give booster shots after eight months rather than six, along with a seeming preference among people for the vaccine developed by Pfizer Inc. and BioNTech SE. But local authorities are now rolling out mass vaccination centers to speed up the rollout, which began Dec. 1 with medical workers, and the government is encouraging so-called cross-vaccinations to get more needles in arms.

Nonetheless, the government has a long way to go to hit its own targets.