Having COVID and the flu: Dr Kylie Quinn answers the top questions about the COVID-19 and flu vaccines and viruses

"I think the key thing about this season as that is going to be quite unpredictable," said Dr Kylie Quinn.

Dr Quinn is the Vice-Chancellor's Research Fellow at RMIT University in Melbourne.

Her area of expertise extends to the seasonal flu and public health measures used to mitigate its effects, particularly in Australia's older population.

Dr Quinn answered some of ACM's biggest questions about the incoming flu season.

Measures to stop the spread of COVID-19 have also proven effective against the spread of seasonal flu.

But with the nation now returning to a 'new normal' without heavy restrictions, experts are worried the flu season may collide with the unfolding rise in COVID-19 cases.

"I think for the past couple of years, the COVID restrictions that we've seen, they have had quite an impact on respiratory infections in general and that has led to fewer flu cases in the community," Dr Quinn said.

As a result, widespread immunity is relatively low.

In the Northern Hemisphere, where the flu season has already started, the emerging evidence suggest "the patterns in flu infection are really disturbed", Dr Quinn explained.

"So usually flu is a very seasonal infection that comes up during winter. Particularly in Australia, it peaks in August," Dr Quinn said.

But, in Australia already, there have been early lab-confirmed instances of flu, which suggests the season could be starting months early.

With dominating strains now emerging alongside COVID-19 infections, the concern is that this season could also nbe unusually long.

"Now we're seeing this resurgence and we're trying to understand when that peak might be. And we're getting hints from the Northern Hemisphere that the it is a very atypical season," Dr Quinn said.

A long and severe season of flu occurred in Australia in 2019 when one type of Influenza Flu B started circulating very early. It was a very lengthy flu season with a high caseload across the health system.

The concern is, that after two years without much influenza, we could be heading for a return to severe seasons like that of 2019.

This is something researchers are currently looking into, but the early evidence suggests it's very unlikely.

Studies have not yet looked at the interplay of flu with Omicron and the emerging Deltacron, but in instances of previous COVID-19 strains, it was less than one per cent who had instances of co-infection.

"But the concern is that the people who are getting co-infection tend to be people who are more at risk of severe disease with with both flu and COVID-19," Dr Quinn said.

"So they tend to be older people. People who are infected tend to need hospitalisation more and ICU admission. And so that's one of the key concerns."

Unfortunately, not at all. The antibodies your body develops from infection will be specific to that infection only. There is no transference of immunity, sadly.

"So when we're talking about immunity with COVID-19, we're talking about mostly about the antibody response that the vaccine or the infection generates and antibodies are these wonderful proteins that are incredibly specific," Dr Quinn said.

"So their job is to be specific. And so they will recognise just one virus and sometimes they will only recognise just one sub-strain of the virus."

If you end up with flu, you can still end up with COVID-19, unfortunately. Though it is unlikely you would have the two viruses at the same time (see above!)

The advice around this question has changed in the past year.

It is now considered safe to have your booster at the same time as your flu shot. In fact, it's now recommended that you do.

"Last year when we were first rolling the COVID-19 vaccines out, people were advised to wait two weeks between their flu vaccine and their COVID vaccine and vice versa," Dr Quinn said.

Now that a lot more is known about the potential side effects of both the flu and the COVID-19 vaccines, it's now safe to co-administer the doses.

There has been discussion over the need for an annual COVID-19 booster shot to deal with the new and emerging virus strains spreading across the world.

If an annual shot is required, then it could be combined with the flu shot.

"Some vaccine designs which are now being developed, particularly the mRNA vaccines, are trying to move in this direction where they have one formulation that contains the vaccine both for influenza and COVID-19," Dr Quinn said.

The challenge this year is to prepare for what will likely be a very unpredictable flu season.

So how do you prepare for unpredictability?

"I think on that individual level, of course, you can prepare for flu specifically," Dr Quinn said.

"There's a lot of things that are helpful for all sorts of different respiratory viruses.

"So things that we've become very familiar with during COVID-19, like not going out into the community when you're symptomatic and sick, and masking where you can, social distancing and all of those sorts of things."