Lead researcher Professor George Milne and his team from UWA’s Department of Computer Science and Software Engineering carried out computer simulation COVID-19 modelling of the highly transmissible Delta variant.

“The key is to be able to get as many people immunised as possible, including kids aged five to eleven in addition to adolescents aged 12 and above,” Professor Milne said. “If not, we’ll still have to introduce lockdowns in some form. The severity of the lockdown is highly dependent on the level of immunity.”

The researchers applied a high-resolution model to evaluate the benefits of adding children as well as adolescents to current COVID-19 vaccination programs, while also determining the reduction in cases, hospitalisations and deaths through moderate lockdown measures.

If the Delta variant entered WA and 90 per cent of adolescents and adults were vaccinated, we could use a moderate lockdown with schools remaining open to effectively control the outbreak, according to Professor Milne.

“But if the vaccination rate was below 90 per cent, modelling indicates we would need to introduce a hard lockdown,” he said.

“Vaccinating adolescents aged 12 to 18 is critical but it’s also important to consider vaccinating children aged five to 11, if current trials in this age group show it’s safe to do so.

“We would also need to provide Pfizer booster vaccinations to those who had received the AstraZeneca vaccine, which had been shown to be less effective at protecting against the Delta strain than other vaccines.”

Professor Milne and colleagues have spent the past 15 years developing disease models, which have been used for several other infectious diseases such as influenza.

The team’s Delta modelling showed that if there was a Delta outbreak in Perth and 80 per cent of Perth residents aged 12 and over were fully vaccinated, we could expect to see around 2,300 people hospitalised and 350 deaths over a three-month period, in the absence of any lockdown measures.

“If we added moderate lockdown measures with schools remaining open, these rates of hospitalisations and deaths would halve,” Professor Milne said. “Vaccinating younger children would also reduce the peak in Delta cases.”

And if 90 per cent of those 12 years and over were fully vaccinated, and moderate lockdown measures activated, the modelling revealed hospitalisations would reduce to 700 with 80 deaths predicted.

The research is funded by the Western Australian and Queensland departments of health.