The CDC said a total of 7.6 million Americans had received the shot as of Sept. 28, the first four weeks the booster has been available. This is up from the 4.4. million people who received the shot as of Sept. 21.
The 7.6 million figure represents only 3.5% of the 215.5 million people in the United States aged 12 or older who are eligible to receive the shots because they have completed their primary vaccination series.
The shots are being administered at a slower pace than last year, when the United States initially authorized COVID boosters just for older and immunocompromised people. Around 12 million people received their third shot in the first four weeks of that vaccination campaign.
As of last week, the U.S. government had sent out over 25 million of the updated booster shots, mostly from Pfizer/BioNTech, as production of Moderna's shot continues to ramp up.
The U.S. Food and Drug Administration authorized Pfizer and Moderna's Omicron-tailored shots last month, in preparation for the country's ongoing fall revaccination campaign.
The CDC tally includes booster shots from both Pfizer/BioNtech and Moderna.
While the Pfizer/BioNTech updated COVID-19 booster is approved for those aged 12 and above, Moderna's shot is approved for individuals aged 18 and above.
The Omicron-tailored shots aim to tackle the BA.5 and BA.4 subvariants, which make up a significant majority of the currently circulating variants in the United States, according to government data.
(Editing by Alistair Bell)