Australians over the age of 18 are now eligible for booster doses five months after their second dose, after the federal government expanded the vaccine program on the weekend.
Moderna also joins Pfizer as a preferred vaccine for booster doses.
Today on Please Explain, explainer reporter Sherryn Groch joins Bianca Hall to discuss how boosters work, and why vaccinating developing countries will be crucial in countering new variants of coronavirus.