Modelling the outbreak till Christmas – Expert Reaction

New modelling sheds light on how the Covid-19 outbreak might spread into early next year, taking into account that more Kiwis will be fully vaccinated.

The Te Pūnaha Matatini report says vaccination could lower virus spread by 67 per cent by early January 2022. However, if there’s high spread of the virus, vaccination and current lockdown restrictions won’t bring down the R number enough to protect NZ’s healthcare system. In this case, the authors say an Alert Level 4 ‘circuit breaker’ in early November could make a major difference. The report is not formally peer reviewed.

The SMC asked experts about the report.

Dr Samik Datta, Population Modeller, NIWA, comments:

“By modelling a variety of factors, researchers have been able to simulate how the COVID-19 outbreak could spread and what its impact on society may be in the near future. This is really useful because it helps us to plan for a range of scenarios. What’s apparent is just how difficult gaining control of the Delta variant really is, but it’s encouraging to see that if we have measures in place, such as a temporary ‘circuit breaker’ lockdown and increased vaccination rates, then hospital burdens would be reduced even if virus transmission rates became high.

“The tool is also beneficial because it factors in age and considers how different groups of people interact with each other – school children mix with each other more than the elderly, for example. This gives a more detailed look at how different sections of society are impacted by the virus’s spread. However, it has a big gap in that ethnicity has not been considered; given the relatively high number of cases in Māori and Pasifika, this will need to be input into future models to ensure we can effectively predict and plan for the months to come.”

Conflict of interest statement: “Samik Datta is part of a review panel (chaired by Dr. Matt Parry) who provide feedback on a range of COVID-19 modelling outputs, and read an earlier version of this report.”

Dr Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Senior Lecturer, Pathology & Molecular Medicine, University of Otago Wellington, comments:

“The modelling work undertaken by Te Pūnaha Matatini simulated the current Delta outbreak in the Auckland Region, from August 2021 through to January 2022, and carefully considered the impact of increased COVID-19 vaccination levels.

“Their work indicated that COVID-19 vaccination could lower the R(eff)value – or model reproduction number by 67 per cent early into January 2022 when compared to the unvaccinated population. The R(eff)value or model reproduction number is the average number of infections caused by a single infection and is a measure of potential disease transmission.

“One of the assumptions applied in this context was that Alert Level 3 restrictions remained in place and maintained effectiveness over time.

“The Te Pūnaha Matatini modelling work also showed that low-transmission scenarios for the SARS-CoV-2 virus combined with ongoing alert level restrictions, could reduce the Reff below 1, as early as November resulting in COVID-19 case numbers that would not add stress our health system.

“However, high-transmission scenarios for the SARS-CoV-2 virus with the current alert level restrictions would not be enough to reduce the Reff below 1 and would likely produce COVID-19 case numbers that would stress and overwhelm our health system capacity.

“The Te Pūnaha Matatini modelling work also showed that a two-week Alert Level 4 ‘circuit breaker” in early November 2021, followed by a return to Alert Level 3 could significantly reduce demands on the health care system all the way through to the beginning of 2022.

“We cannot allow our Health System in Aotearoa New Zealand to become overwhelmed, as it was already under strain and burdened even before the COVID-19 Pandemic began.

“Vaccination is key right now.

“As has already been demonstrated, our Māori and Pacific communities remain highly vulnerable to being disproportionately affected by COVID-19 and will likely bear the heavy burden and toll of any further outbreaks.

“To ensure no-one is left behind, vaccination target details for Aotearoa New Zealand needed to include at least 90 – 95 per cent full vaccinations for Māori and Pacific peoples. This would help keep our most vulnerable communities safe from COVID-19 – and also includes protecting our children and young people.”

No conflict of interest.