While the coronavirus growth rate has slowed over the past few days, there's still likely to be cases circling in the community undetected.

Community transmission hotspots are popping up in suburbs in Sydney and Melbourne.

So how many unknown COVID-19 cases could there be out there?

In today's episode:

* Flu shots. Why get one?

* Should I bunker down or risk venturing out to get a flu vaccine?

* How reliable is COVID-19 testing anyway?

And Dr Norman Swan explains the research from America which might give an indication of how many undetected cases are out in the community.