New variants could mean 11,000 cases daily

Modelling suggests Covid-19 numbers could rise to a peak of 11,000 cases per day next month if new variants drive a third wave.

Data released by the Ministry of Health and Covid-19 Modelling Aotearoa yesterday considered possible higher case levels due to the potential impact of new variants. A handful of subvariants are in the community, including BA.2, BA.2.75, BA.4.6, BQ.1.1, BA.5 and XBB.

Given a lack of real-world information about these subvariants, many assumptions for the modelling were borrowed from those used for the BA.5 wave – assuming the new variants have a combined growth rate of 10%.

Based on these assumptions, daily case numbers could rise to a level similar to the July peak – with about 11,000 cases reported per day, the report stated.

However, since this ‘‘midpoint scenario’’ was modelled, more people were infected in September and October than initially expected. This meant a following wave could be ‘‘lower and slower’’, as more people had immunity than the model assumed, Covid-19 Modelling Aotearoa’s Dr Dion O’Neale said.

Under these assumptions, daily Covid hospital admissions could peak at just over 100 a day – slightly higher than the July peak (but in line with assumptions around the BA.5 wave). This could also see Covid deaths peak at a similar level to the July peak.

Modelling was unable to provide a ‘‘reliable estimate of the timing of the peak’’ – given the uncertainty around the growth rate in an Aotearoa context.

The modelling – done about a month ago – is not a prediction, and has a high level of uncertainty, given the unpredictable impact of new variants, population immunity and antiviral medicine use, which would further reduce hospitalisation and death. ‘‘We cannot know at this stage if the new variants will translate into increases in cases or hospitalisations, and previously actual case numbers have been lower than modelled,’’ the report stated. In reality, the impact of these new variants had varied between countries – with some experiencing relatively small increases in cases, it said.

In the past week, to November 6, Covid-19 cases and hospitalisations have stabilised. There were currently about 397 cases per 100,000 people, a 1% increase from the previous week (ending October 30). This follows a previous 25% rise week-on-week.