Executive summary

  • We use a branching process model to simulate the Auckland August 2021 outbreak through to early January 2022, including the effects of increasing vaccine coverage by age group and time.
  • Based on vaccination data and bookings for the Auckland metro region, we estimate that vaccination reduces the model reproduction number by approximately 67% relative to an unvaccinated population by early January 2022.
  • We assume that Alert Level 3 controls are held in place and that the effect of these controls does not diminish over time. Effective contact tracing capacity is set at 1,000 active cases.
  • In low-transmission scenarios, vaccination in tandem with sustained alert level restrictions is sufficient to bring Reff <1 in November. These scenarios generally lead to case numbers that are likely to be manageable within existing health system capacity.
  • In high-transmission scenarios, vaccination and current alert level restrictions are not sufficient to bring Reff <1 during 2021. These scenarios generally lead to case numbers that would place extreme demands on health system capacity.
  • In the high-transmission scenario, an effective two-week Alert Level 4 ‘circuit breaker’ in early November followed by a return to Alert Level 3 can significantly reduce demand on the health care system through to the beginning of 2022.