Sadly, greater Sydney and surrounding areas are to spend another week in lockdown after COVID-19 cases have refused to come down to more comfortable levels.

The NSW Premier Gladys Berejiklian has warned cases today will likely also be high, and that additional restrictions may need to be imposed.

So on today's Coronacast, why do authorities need more time? And what can we tell about the Delta variant from the cases so far?

Also on today's show:

* Is the number of people in ICU in the Sydney outbreak unusually high?

* Why isn't Dr Norman Swan having a second AstraZeneca shot now that it's 8 weeks after his very public first shot?

* We hear a lot about the Delta variant and now Kappa and Lambda variants. Were there variants in between that got named?