When to expect our next COVID-19 wave — and what could cause cases to spike

Two key factors will determine how severe the next COVID-19 wave will be, according to experts.

Many cases no longer present with typical COVID-19 symptoms, experts say. Source: AAP / JANE DEMPSTER/AAPIMAGE

Key Points

• Australians copped a double COVID-19 wave over summer, with numbers still on the decline.
• Experts have identified two factors that could cause a spike in case numbers or prompt the "next wave".
• They warn a previous COVID-19 infection is not enough to keep you safe, with boosters the best form of protection.

As a cool change rolls in, Australians can brace themselves for another wave of the COVID-19 virus.

Four years into the pandemic, vaccination remains the best way to protect Australians from severe disease, experts say. But there's concern many older people, who are at greatest risk of serious symptoms, are not up-to-date with their boosters.

Epidemiologists told SBS News what challenges lie ahead this winter.

When can we expect the next wave to start?

Waves are hard to model but certain trends are evident, said Catherine Bennett, Deakin University's chair of epidemiology.

She predicted this year's winter wave might hit us in June or July, a bit later than in 2023 as numbers are still declining following a "double wave over the summer".

The epidemiologist noted that we've also seen longer breaks between waves, with a shift from three to two waves per year, but that each one comes "at a cost".

"Thankfully when we see waves, if they're coming further apart, we have more reprieve between, but also we see fewer people becoming seriously ill in each wave," she said.

"It still means there are people who are vulnerable to serious infection and unfortunately we have still seen people pass away. But the peak number of deaths has also continued to decline."

She noted that hospitalisation and ICU rates were also decreasing.

What might determine how bad the next COVID-19 wave gets?

Adrian Esterman, chair of epidemiology at the University of South Australia, said two factors will impact the wave's severity: "new sub-variants and people's immune status".

Of particular concern is the BA.2.87.1 variant detected by scientists in South Africa.

Although currently isolated to the region, the variant represents a significant shift, with roughly 30 changes to its protein spike.

"If and when it mutates, that will almost certainly take off and could be the next wave," Esterman told SBS News, with current vaccines not based on these variations.

He highlighted low booster numbers are another possible challenge, with many at-risk Australians aged 75 years and over not up to date with their vaccines.

"They're our big vulnerable population group and they are under-vaccinated," he said.

The federal government updated its COVID-19 vaccination guidelines last month after it accepted advice from the Australian Technical Advisory Group on Immunisation (ATAGI).

Anyone aged 65 and old, and severely immunocompromised Australians between 18 and 64 years old are strongly encouraged to get a booster vaccine every six months.

If you've had COVID-19, you are not immune

Bennett said it's important to keep up boosters as they offer "extra protection".

She warned one COVID-19 infection is not enough to keep you safe.

"I do think it's still important because while they don't prevent infection, they can reduce your risk of having any infection," she said.

There's concern many older people, who are at greatest risk of serious symptoms, are not up-to-date with their boosters. Source: AAP / Joel Carrett

When should I get a booster shot?

Bennett said you can hold off your booster a little longer unless you're in a high-risk group.

She said you should get your shot as infection numbers rise, probably in May.

"When you start to see a consistent kick up over a couple of weeks, numbers will still be low, but it gives you enough warning that they're probably going to keep rising," she said.

Timing the booster will also increase your protection during the height of the wave.

"You will have a less likelihood of having an infection in those at critical first one to two months. That's when you get the best benefit from a booster," she said.

Bennett said wearing a mask in public places, including public transport, is still the most important way of reducing the likelihood of infection when the risk of exposure is rising in a wave.

Both experts stressed that almost half of cases no longer present with typical COVID-19 symptoms, or no symptoms at all.

But if present, avoid spreading the virus by wearing a mask, practicing good hygiene, hand washing, reducing touching surfaces, and working from home.

The most recent COVID-19 surveillance reports, testing the state's wastewater, show low viral loads in NSW and Victoria.