It's well known by now that you need to have both doses of whatever vaccine you have for the best possible protection against coronavirus.

But what if it actually takes three shots to get there?

We are learning more and more about immunity against COVID-19 from overseas experiences, including a successful booster program in Israel.

So might the ol' two dose vaccine regime actually take three? That's on today's Coronacast.

There are to be no large changes to Victoria's lockdown restrictions, after a large jump in cases overnight and Government acceptance that the Delta outbreak can't be brought back to zero.

Apart from some small changes, such as reopening playgrounds, people in Melbourne will remain in lockdown until vaccine levels get high enough.

But that's not to say the lockdown in both Victoria and NSW has been without success. Modelling has shown many tens of thousands of cases have been prevented with the extreme social distancing.

So on today's Coronacast, what happened in Victoria and what could it mean for other states?

Also on today's show:

* An interesting study from Hong Kong on eye sight and lockdowns.

* My kid's best friends come from a family that's vehemently opposed to the vaccine. We hang out all the time. I'm not going to convince them and I don't want to stop being with them but I'm concerned there is additional risk there for us. What should I do?

The Victorian Government will today announce details around how it plans to manage COVID-19 cases as it rushes to vaccinate as many people as possible.

Yesterday, Premier Daniel Andrews said he'd be meeting with health officials to develop thresholds for the easing of the lockdown, where possible.

It's a move away from the COVID-zero goal of the past, as it appears unlikely that the state will manage to eliminate the spread of the Delta variant.

So on today's Coronacast, is this a new medium term strategy of balancing caseloads with the hope enough people will be vaccinated before the health system crumbles?

Also on today's show:

* Is there any research on having a mRNA shot first followed by Astra in terms of efficacy and safety?

* An interesting study on COVID-19 and immune-mediated inflammatory diseases

It was another record day yesterday for NSW in COVID-19 cases, and the wave is showing no signs of slowing down.

And yesterday in even more grim news, the Premier Gladys Berejiklian flagged that October would be the worst month for hospitals and ICU units.

That's despite the vaccination rate in NSW charging ahead thanks to a population rushing forward to be vaccinated and additional supply helping things out.

So on today's Coronacast, why is October being tipped to be bad when the vaccine rate is growing so quickly?

Also on today's show:

* What can we learn about long-COVID from the people who've lived with it longest?

* I am confused by the target of 70 to 80 per cent immunisation before opening up. There is a very big difference between 70 and 80. Can you explain please?

* What's the likelihood that our third doses of mRNA vaccine will have been changed to specifically target the Delta variant?

Case numbers in both Victoria and NSW continue to climb, with both states yesterday posting new daily records for this year.

While Victoria's daily cases are far behind NSW, Victoria is on a similar trajectory as NSW was - despite locking down hard and early.

So what's going on? Why are cases continuing to rise?

Also on today's show:

* ATAGI recommends vaccinations for 12-15 year olds

* With kids getting the vaccines, what will that mean for the 70/80 per cent targets (as more people are now getting vaccinated)

* What is the likelihood of an even more transmissible or deadly strain emerging and what should we be doing to be ready for it?

Fully vaccinated NSW residents will be given a very small increase in freedoms, after the state reached more than 6 million vaccination doses earlier this week.

The state's Premier Gladys Berejiklian yesterday revealed that from mid-September, people who are fully vaccinated will be able to meet more people or spend more time outdoors - depending on where they live.

But it wasn't all good news, with the state revealing more than 1000 new COVID-19 cases - the highest it's been in Australia at any point of the pandemic.

So on today's Coronacast, is this a turning point in how lockdowns operate as we move on from trying to eliminate COVID spread?

Also on today's show:

* How are we supposed to keep following the rules when we get nothing in return?

* Please tell us about Lambda and AY3. Should we be concerned?

You might have heard a friend or family member say 'I'm waiting for Pfizer', on the assumption that the mRNA vaccine works better than others.

But according to a recent study from the University of Oxford, immunity from the Pfizer vaccine may actually start to wane faster than AstraZeneca.

A month ago, Israel began a program of booster shots, giving older people a third shot of the vaccine to try and help tame a growing outbreak of the Delta variant.

So on today's Coronacast, what do we know about how long immunity may last?

Also on today's show:

* What effect would it have on our community if those who are fully vaccinated were given some benefits, such as reduced restrictions?

* When do we stop contact tracing altogether?

The Doherty Institute Model is the hottest ticket in town, with everyone from politicians to punters talking about what happens when we reach 70 and 80 per cent vaccination levels.

But there are a lot of assumptions that have to be made to come up with a model, and Doherty Institute's plan is no different.

Among other things, it assumes a certain level of cases, a functioning contact tracing system even at high numbers and vaccines that keep us immune to COVID-19.

But on today's Coronacast, how valid are those assumptions in the real world?