With Australia's two biggest cities now in lockdown, you'd be forgiven for wondering when is this all going to end.

Lockdowns are an incredibly blunt tool to control pandemics, but in many cases - if you want to keep control over spread - they're one of the only options available.

Yesterday, Melbourne joined Sydney in locking down thanks to the highly infectious Delta variant, which continues to put pressure on Australia's pandemic response.

So on today's Coronacast, what is the point of a lockdown? And are they worth it?

Also on today's show:

* University of Sydney modelling looks at Sydney's response

* Symptoms to keep an eye out for after AstraZeneca vaccination

And it's time for Quick Fire Friday! (Because it's Friday)