A preliminary assessment of the potential impact of the Omicron variant of SARS-CoV-2 in Aotearoa New Zealand

Executive summary

• The results in this report are a preliminary assessment of the potential impact of Omicron in New Zealand and are subject to significant uncertainty. This modelling was carried out before the detection of the Omicron outbreak on 23 January 2022. Modelling will need to be updated once sufficient local data is available.
• For an outbreak starting around 1 February, in scenarios where there is high booster uptake, peak hospital admissions range from 200 to 800 per day, and peak demand for hospital beds ranges from 800 to 3,300 depending on assumed transmission rates.
• These numbers would put significant strain on hospital capacity. Thus, under these scenarios, public health measures may be necessary to flatten the curve and avoid overwhelming the healthcare system.
• Due to the effects of waning immunity and the ongoing booster rollout, different groups will have different levels of risk at different times. Groups that are not yet eligible for the booster will be at elevated risk of severe illness.
• In general, lower booster uptake leads to worse outcomes. Slowing an outbreak to allow time for more people to receive their booster doses is a strategy that could reduce the overall health burden.
• However, the waning of immunity presents a danger that health outcomes in groups that were earliest to receive their booster become worse after a longer time period. Thus outbreaks that occur after significant waning of immunity can result in a higher overall health burden compared to outbreaks that occur during peak immunity. Maintaining high immunity levels across all groups will be important for future vaccination strategies.

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