“Immunity debt” is the idea that there is increased infectious disease now, because there was less circulation of pathogens due to lockdowns some years ago. It is not a validated scientific phenomenon.

Increased illness is to be expected following a new pandemic, and there is good evidence that the SARS-Cov-2 virus damages immune response to other diseases subsequently.

Lockdowns everywhere, and in Australia in particular, were not of sufficient duration or rigour to affect immunity on a population level. They were typically brief and incomplete in terms of preventing human contact.

Credit @ragesheen