CANBERRA, Dec. 24 (Xinhua) -- Australia has reduced the booster shot interval for COVID-19 vaccines in response to nationwide Omicron outbreaks.

The Australian Technical Advisory Group on Immunization (ATAGI) on Friday announced that from Jan. 4, Australians aged 18 and over will be eligible to receive their COVID-19 vaccine booster four months after the second dose, down from five months currently.

From the end of January, the recommended interval will be reduced again to three months.

It came after state and territory leaders called for the interval to be slashed to curb the rapid spread of the Omicron variant across the country.

Health Minister Greg Hunt said the changes mean 16 million Australians will be eligible for booster vaccines by the end of January.

"These dates have been set out of an abundance of caution to give Australians early continued protection and the advice we have is that the protection, as it is, is very strong against severe illness, but what we'll see is a much stronger protection against transmission," he told reporters.

Pfizer and Moderna's mRNA vaccines are the only COVID-19 vaccines currently approved for use as boosters in Australia.

Chief Medical Officer (CMO) Paul Kelly said protection for people who have had two vaccine doses will not disappear suddenly but that boosters would offer an extra level of security.

"We know that unfortunately, two doses does not change that ability to become infected a great deal. Again it wanes over time," he said.

"That protection against infection is diminished against Omicron, that's quite clear, but again with a booster it goes back towards the same levels as Delta."

Australia on Friday morning reported a new record 9,113 COVID-19 infections and nine deaths.

The Australian Capital Territory (ACT) recorded 102 new COVID-19 cases on Friday, the first day of triple-digit case numbers in the territory since the beginning of the pandemic.

South Australia (SA), which reported a pandemic-high 688 new cases, has lifted a ban on the sale of rapid antigen tests (RATs) in a bid to relieve extreme pressure on testing sites in the lead-up to Christmas Day.