Pertussis notifications decline in Australia during COVID-19 non-pharmaceutical interventions, 2020-2021.

Background: Following implementation of coronavirus diseases 2019 (COVID-19) non-pharmaceutical interventions (NPIs) in early 2020, declines in the incidence of other respiratory pathogens have been reported. This study aimed to assess the impact of these interventions on pertussis notifications in Australia.

Methods: We compared monthly national notification rates for pertussis during the first two years of the COVID-19 pandemic (2020 and 2021) to those during the three pre-pandemic years (2017 to 2019). Incidence rate ratios (IRR) by age group and jurisdiction were calculated for 2020 and 2021 compared to the mean prepandemic annual notification rate.

Results: A substantial progressive decline in pertussis notifications was seen across all age groups, with all-age notification rates more than 40% lower than the pre-pandemic period in all jurisdictions in 2020, and more than 80% lower in 2021. Notification rates decreased more slowly from a lower baseline in Victoria than in other states and territories, despite the stricter, more sustained NPIs implemented in Victoria.

Conclusion: The significant decrease in pertussis notifications across all jurisdictions and age groups has likely resulted in reduced infection-acquired immunity, making maintenance of high vaccine uptake, particularly among pregnant women and young infants, of key importance.