How might the new strains of COVID-19 impact the upcoming winter season?

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Key Points

The mortality rate for COVID-19 has steadily declined since 2023.
Experts say vaccinations and medicines have reduced the severity and lethality of the virus.
But some warn the virus can be unpredictable.

The number of Australians dying from COVID-19 continues to decline — but experts have warned against complacency.

Mortality data from the Australian Bureau of Statistics (ABS) released last week shows that deaths from COVID-19 have steadily declined since 2023.

The number of people dying with COVID-19 — where it is deemed not the primary cause of death — is also decreasing.

However, experts have pointed to the unpredictability of the virus and the common rise in infections that occur during the winter months to warn against complacency.

What does the data show?

The latest ABS provisional mortality statistics report gives a snapshot of COVID-19 deaths as certified by doctors and coroners.

The data may not be perfect, as the cause of death can be complex, but it suggests deaths from COVID-19 have dropped dramatically.

In 2023, there were 4,609 deaths from COVID-19, and last year, there were 3,871 deaths from COVID-19 recorded.

Data from the first four months of 2025 indicate 514 COVID-19-related deaths so far this year.

Paul Griffin, an associate professor of medicine at the University of Queensland, who has also run clinical trials for COVID-19 vaccinations, said it’s great news that mortality rates are declining.

“This is likely due to the availability of oral anti-viral medications, vaccinations and greater understanding COVID-19,” he told SBS News.

“As health professionals, it’s clearly great to see less people dying from COVID-19, but it’s important to look at that in context.

“There are still a number of people who get very sick, and the effects of long-COVID-19 can be debilitating.”

Griffin said experts are still working to understand how COVID-19 adapts and changes, and what the long-term health impacts could be.

While the downward trend in mortality is “encouraging,” he cautioned that the virus remains “very unpredictable”.

‘Still a lot we don’t know’

Griffin explained that COVID-19 can mutate, with new strains emerging frequently.

“Just recently we’ve seen a new strain: NB.1.8.1, which seems to have different characteristics from other variants,” he said.

“When it comes to predicting the future of COVID-19, in terms of severity and mortality, I would be reluctant to say the decreasing rates of mortality will continue.

“There’s still a lot we don’t know.”

The mortality data from previous years indicates that COVID-19 deaths increase from May to July — data yet to be collected for this year.

Catherine Bennett, chair in epidemiology at Deakin University, said there were a range of ways emerging strains of COVID-19 can impact people.

“COVID can be different from one infection to the next in the same person,” she said.

“The other important thing to remember is long COVID, and we don’t have good data now and we don’t know if our immunity is helping protect us from long COVID.”

Now is a good time to consider vaccination

While long-term immunity from multiple boosters is hard to measure, Bennett emphasised the importance of vaccines, particularly now as winter sets in.

“It takes a couple of weeks to get the best out of a vaccine to actually get that boosting happening,” she said.

“And equally, the vaccines last a couple of months. It’s when they have their greatest impact and six to eight weeks is the usual duration for our waves.

“So, actually, having a vaccine now as winter comes is the right time.”

Bennett said that a low number of COVID-19 cases in the summer months of 2025 could mean there may be a higher number of infections this winter, as people will be less resistant to the virus.

“It’s a sad irony that a quiet summer in infections may lead us to seeing more people exposed in winter,” she said.

She said the more people that get vaccinated, the better the public health outcomes would be, especially for vulnerable groups.

A 2024 report from the National Centre for Immunisation Research and Surveillance found that children aged from 12 months to 5 years old had lower vaccination rates in 2023 than in 2020.

Mortality is higher in winter months

Griffin explained that the mortality rates of viruses like COVID-19 and influenza increases in winter for two main reasons.

Firstly, they can survive longer in winter months when there is decreased sunlight, lower temperatures, and lower relative humidity.

The other factor is human behaviour.

“When it is colder, people are more likely to be indoors and in closer proximity to others. There can also be decreased ventilation and airflow as people may close windows to keep the cold out,” he said.

“Large indoor gatherings can be a hotbed for the flu and COVID-19.”

His advice is to ventilate where possible with airflow and air purifiers, and to avoid other people when you have flu-like symptoms such as a cough or sore throat.