ATAGI recommends an additional booster dose of COVID-19 vaccine to increase vaccine protection before winter for selected population groups who are at greatest risk of severe illness from COVID-19 and who have received their primary vaccination and first booster dose. These groups are:

• Adults aged 65 years and older

• Residents of aged care or disability care facilities

• People aged 16 years and older with severe immunocompromise (as defined in the  ATAGI statement on the use of a 3rd primary dose of COVID-19 vaccine in individuals who are severely immunocompromised)

• Aboriginal and Torres Strait Islander people aged 50 years and older.

More information is available here: https://www.health.gov.au/news/atagi-statement-on-recommendations-on-a-winter-booster-dose-of-covid-19-vaccine