Executive summary

  • The BA.5 Omicron sub-variant is able to spread more easily than the previously dominant BA.2 sub-variant due to its immune escape characteristics. This is a key driver of the second Omicron wave in New Zealand in July/August 2022.
  • Updated modelling results that take into account new evidence for the strength of hybrid immunity suggested that the peak in new daily cases would be smaller than the peak of the first Omicron wave in March 2022.
  • Leading up to the second Omicron wave, the age distribution of cases shifted into older age groups where there is a larger susceptible population, most likely due to relatively low attack rates in the previous wave. As a result of this, the model suggested that even though daily cases were likely to peak at a level below the first Omicron wave, the peak hospital occupancy and the number of deaths could be higher than in the first Omicron wave.
  • These results suggested that public health measures such as strong uptake of booster doses, masks, widespread testing, case isolation, and ventilation would be important to reduce the load on the healthcare system through the remainder of the winter period.

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