Australia unlikely to fully reopen borders in 2021 as virus cases slide

* Australia recorded zero local coronavirus cases

* Four new cases in overseas travellers linked to Aust Open

* Australia looking into Pfizer vaccine deaths in Norway

By Swati Pandey

SYDNEY, Jan 18 (Reuters) - Australia may not fully reopen its international borders this year even if most of the population is vaccinated against coronavirus, the head of its health department said on Monday as the country recorded zero local COVID-19 cases.

Australian authorities are also looking at potential adverse effects of the Pfizer vaccine after Norway reported a small number of deaths in old people who received the shot.

"Even if we have a lot of the population vaccinated, we don't know whether that will prevent transmission of the virus," Brendan Murphy told the Australian Broadcasting Corp.

Australia, which has managed the coronavirus better than many other nations through targeted lockdowns and high rates of testing and contact tracing, reported zero local COVID-19 cases on Monday.

Victoria, which is hosting the Australian Open, reported four positive cases in overseas travellers, all associated with the tennis, taking the total to nine.

The cases have prompted authorities to send three Australian Open charter flights into hard quarantine, forcing more than 70 players into a 14-day hotel room isolation.

"I know that there's been a bit of chatter from a number of players about the rules. Well, the rules apply to them as they apply to everybody else," Victorian state Premier Daniel Andrews said, responding to player complains about the strict quarantine.

Australia has reported more than 22,000 local COVID-19 cases and 909 deaths since the pandemic began. (Graphic: )

The main COVID focus in Australia is currently in Sydney in the state of New South Wales (NSW), where an outbreak in Sydney's west has prompted other states to impose travel restrictions on either all of NSW or people in outbreak suburbs.

NSW state Premier Gladys Berejiklian said she would consider permitting venues to ban entry to people who have not been vaccinated against COVID-19.

Australia will begin its immunisation programme next month.

"Already airlines have indicated that if you’re not vaccinated you can’t travel overseas and I think that’ll be incentive to a lot of people," Berejiklian told 2GB Radio.

"We’ll also consider whether we allow venues ... make up their own rules if they have a business or run a workplace about what they feel is COVID safe."

(Reporting by Swati Pandey; Editing by Michael Perry)

((swati.pandey@thomsonreuters.com; +61 2 9321 8166; Reuters Messaging: twitter.com/swatisays))