A new opportunity for some groups to improve their immunity against Covid-19

From today, a second booster will be available for those over 50, health, aged care and disability workers over 30, and those who are severely immunocompromised

They will be able to get the jab six months after their first booster.

Immunologist Graham Le Gros says it's a necessary move.

He says from four months after your first booster, immunity begins to wane.