Temporal associations of the COVID-19 related border restrictions and respiratory viral infections in New Zealand

Abstract New Zealand (NZ)’s elimination of community transmission of influenza and respiratory syncytial virus (RSV) infections in May 2020, due to stringent COVID-19 countermeasures, provided a rare opportunity to assess the impact of border restrictions and relaxations on common respiratory viral infections over the subsequent two-years. Using multiple surveillance systems, we observed that border closure to most non-residents, and mandatory government-managed isolation and quarantine on arrival for those allowed to enter, appeared to be effective in keeping influenza and RSV infections out of the NZ community. Partial border relaxations through quarantine free travel with Australia and other countries were associated, within weeks, with importation of RSV and influenza into NZ in 2021 and 2022. Border restrictions did not have effect on community transmission of other respiratory viruses such as rhinovirus and parainfluenza virus type 1. These data can inform future pandemic influenza preparedness as well as provide insights into effective strategies to plan and model the impact of seasonal influenza, RSV, and other respiratory viral infections.