Canberra, Dec 12 (IANS): Australia's expert panel on immunisations announced on Sunday that it has shortened the recommended wait time for the coronavirus booster vaccines.

The Australian Technical Advisory Group on Immunizations (ATAGI) said that the interval between the second and booster shots for people over 18 has been cut from six months to five, reports Xinhua news agency.

The change means approximately 1.5 million more Australians are now eligible for booster shots.

The ATAGI also confirmed it had approved Moderna's vaccine as a booster shot and an alternative to the Pfizer dose.

The emergence of the Omicron variant has made boosters "much more important," said Secretary of the Department of Health Brendan Murphy.

"We do believe that, as one gets towards six months, the waning immunity of the primary vaccination means that a booster will be very important to continue that protection against this variant," he told reporters.

"We are still protected with our primary vaccination; people shouldn't be worried," he added.

Till date, 93.3 per cent of Australians aged 16 and over had received at least one coronavirus vaccine dose, and 89.2 per cent were fully inoculated.

Health Minister Greg Hunt said 683,000 people had received booster vaccines so far -- a figure he said was "well ahead" of the government's expectations.

Australia on Sunday reported more than 1,500 new locally-acquired Covid-19 infections and four deaths.

Meanwhile, authorities in South Australia have confirmed the state's first two cases of the Omicron variant, and contacts of the cases have been forced into quarantine for 14 days regardless of their vaccination status.