Raina MacIntyre, head of the biosecurity program at the UNSW's Kirby Institute, said allowing people to be infected was an "extremely dangerous" strategy and a breach of medical ethics that would put vulnerable people at risk.

To achieve herd immunity - meaning enough people become immune to a virus through exposure that its spread is thwarted - required between 55 and 60 per cent of a population to be infected, she said.READ MORE