WASHINGTON - Around 3.9 million people in the United States received updated Covid-19 booster shots over the past week, the Centres for Disease Control and Prevention (CDC) said on Thursday.

The CDC said a total of 11.5 million Americans had received the shot as of Oct 5, the first five weeks the booster has been available.

This is up from the 7.6 million people who received the shot as of Sept 28.

The 11.5-million figure represents only 5.3 per cent 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 authorised Covid-19 boosters just for older and immunocompromised people.

Around 20 million people received their third shot in the first five weeks of that vaccination campaign.

A recent survey conducted by the non-profit Kaiser Family Foundation found that nearly two-thirds of adults in the United States do not plan to get updated Covid-19 booster shots soon.

The US Food and Drug Administration authorised Pfizer and Moderna's Omicron-tailored shots in August 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.

These Omicron-tailored shots aim to tackle the BA.5 subvariants, which makes up a significant majority of the currently circulating variants in the United States, according to government data. These shots are expected to also be effective against the slowly rising BA.4.6 subvariant. REUTERS