Australian state governments are tinkering with how “fully vaccinated” individuals are defined, with booster shot mandates now inching across four states. Western Australia was the earliest jurisdiction to make the COVID-19 booster shot mandatory for its million-strong workforce in a directive issued on Dec. 22—on top of an existing vaccine mandate. “The emergence of Omicron throughout the world and on the east coast is extremely concerning—case numbers are skyrocketing, as is the number of people in hospital,” Premier Mark McGowan told reporters. New South Wales, Victoria, and South Australia have followed suit, introducing targeted booster mandates. Healthcare workers in South Australia will need to have a booster shot within four weeks of becoming eligible (pdf). Currently, Pfizer and Moderna boosters have been approved for use by Australian drug regulators. On Jan. 10, Australia’s most populous state, New South Wales, ordered all education staff to receive the booster. The announcement came …