There's been a rather large jump in the number of COVID-19 cases in Sydney, with the cluster growing beyond 20 people.

While the majority of the cases reported yesterday were already in isolation, there was at least one mystery case in which contract tracers have had to hunt down the source.

The NSW Government has mandated the use of masks on public transport and in all public indoor venues Sydney wide.

So on today's Coronacast, why there hasn't been a lockdown in Sydney so far.

Also on today's show:

* Living with lockdowns over the next several months

* Possible surface transmission in Queensland

* What effect does vaccination have on pregnancy?

* Should I breastfeed after I've been vaccinated?