There was a large jump in COVID cases in NSW yesterday, and while we're largely moving on from day to day case numbers - this one is worth talking about.

Why? Well, there's a new variant in town and health authorities are already suggesting that we can expect far more from Omicron in coming weeks.

The same goes for other states and territories - like Victoria which still has higher daily figures than NSW, but hasn't yet seen a big jump.

So on today's Coronacast what should we make of the rising caseload and does it matter?

Also on today's show:

* A deeper look at what's going on in South Africa

* An announcement on Coronacast for 2022!

After nearly two years of constant internal border changes, by the end of this week large parts of Australia will once again be open for domestic travel.

South Australia opened a few weeks ago, Queensland opened yesterday and Tasmania is due to open tomorrow.

Western Australia has also finally given a date and will reopen on the 5th of February next year.

So with state and territory bubbles bursting all over the place, what might come next for people who live there?

Also on today's show:

* How is decoupling going?

* Fourth dose anyone?

* Pregnancy and booster shots

Australia now has two different booster options to choose from when the inevitable time comes for the third dose of coronavirus vaccine.

Moderna was approved by the country's vaccine expert group ATAGI over the weekend.

We'll also be able to get the booster a month earlier, with the Government announcing a shorter period due to the threat of waning immunity and new variants.

So if Moderna is a choice, should you take it over Pfizer? Does it even matter? And why is the Moderna booster only a half shot?

Also on today's show:

* A preprint study has found that Astra seems to wane faster than other vaccines, leaving no protective effect against symptomatic disease from Omicron 15 weeks after the second dose. What could this mean for the country's booster campaign?

As the data from initial studies into how Omicron evades our immunity continue to flow in, it's becoming more and more likely that a third dose - or booster - is going to be essential.

Several more studies have been released, all showing large falls in immunity to the Omicron variant.

One thing that the studies imply though is that there are much higher antibody levels in people who have either been infected, or received a third dose.

So how much will third doses be needed to combat Omicron?

Also on today's show:

Quick Fire Friday! (booster edition)

One of the first studies into Omicron and immunity has reported back and it's not super great news: there's significant evasion of antibodies produced by the Pfizer vaccine.

But not all is lost. The study says that the Omicron variant uses the same way of getting into our cells, meaning our existing tools and techniques should be relatively easy to change so they work better.

The study is not yet published, and is a very small sample size so it's worth keeping in mind that this is still a very new area of science and is subject to change.

Nonetheless, as today's Coronacast explains, it does give us a glimpse of what is likely to come.

Also on today's show:

* Could a mozzie vaccinate someone by biting a vaxed person and then an unvaxed person?

* Your booster experiences

Beyond the nasty and sometimes life-threatening symptoms that COVID can bring, there's another risk: long COVID.

It's the collection of prolonged symptoms including brain fog, smell loss and fatigue.

And while we know that being vaccinated drastically reduces your risk of a bad bout of COVID itself, a lingering question has been whether it also protects you from long COVID.

Well, according to a yet to be peer reviewed study, the answer is yes it does.

Also on today's show:

* Is there any research work being done to modify the virus to develop a relatively benign but transmissible COVID variant which could be released to "crowd out" the current dangerous variants?

* Is there a chance that Omicron is different enough that instead of replacing Delta, you get both if not together then one after another?

* And we're after your stories about getting third-doses. Was it easy? Or hard?

Over the next several months, the fight between Delta and Omicron is going to be scientifically fascinating.

In the red corner is the current world champion Delta, which easily beat out every other variant of concern to date.

In the blue corner is the challenger Omicron, whose continued existence probably relies on its ability to beat out the champion.

But how will we know who's winning and when will we get a better sense of it all?

Also on today's show:

* What makes a virus go viral?

* Who decides which variants you make vaccines for?

* What happens if Omicron turns up in a place with no Delta (like Queensland or Tasmania, for example)?

It's been a bit more than a week since we learned of Omicron, the newest coronavirus variant of concern.

And while we're still a while from knowing solid answers, the world's scientists have done an amazing job over the last 7 days unraveling parts of Omicron's mysteries.

The three big questions are will our vaccines continue to work? For people who do get the virus, will it be severe and will it beat Delta to become the coronavirus champion of the world?

So on today's Coronacast, what we know from the latest science about answering those big questions.

Also on today's show

* Does it escape previous immunity and/or our vaccines?

* Is it better at spreading than Delta?

* Does it matter? Does it make you sicker than previous variants?

* Where's Dr Norman Swan's Omicronometer of Panic heading?

Just like we're likely going to be stuck with COVID for the rest of our lives, we're probably also going to be stuck wondering which is the most effective vaccine to protect against it.

Well lucky we've got science to help sort it out, with a new study putting the Moderna and Pfizer vaccines head-to-head across hundreds of thousands of people.

And other scientists have been busy working out how much protection you have against reinfection, if you are infected in the first place.

Also on today's show:

* Quick Fire Friday

* Tegan interrupts Quick Fire Friday with her own - excellent - Quick Fire Question.