Updated COVID-19 boosters have gone into 4.4 million arms in the United States since a new revaccination campaign began three weeks ago, government data shows, a slower pace for the shots targeting the omicron variant of the coronavirus than the rollout of the first boosters last year.

The government said earlier this week it has shipped 25 million of the omicron-tailored shots, mostly from Pfizer/BioNTech.