Notifications decline in pertussis, invasive pneumococcal disease, and invasive meningococcal disease following COVID-19: the potential impact of nonpharmaceutical interventions in Australian states and territories
Background: Following the implementation of COVID-19 nonpharmaceutical interventions (NPIs) in early 2020, substantial declines in notifications of other respiratory pathogens, particularly influenza, have been reported. This study aimed to determine any impact of these measures on pertussis, invasive pneumococcal disease (IPD), and invasive meningococcal disease (IMD) in Australia.
Methods: This study examined notification trends for pertussis, IPD, and IMD in Australian states and territories during the COVID-19 pandemic (2020 and 2021) compared to previous years. For pertussis, the pre-pandemic comparison period was 2017 to 2019. For IPD and IMD, the pre-pandemic comparison period was 2015 to 2019 (2017 was excluded for IMD). For each disease and jurisdiction, monthly notifications for 2020 and 2021 were compared to mean monthly notifications for the pre-pandemic period. Incidence rate ratios were calculated for the annual notification rate for 2020 and 2021 compared to the prepandemic mean annual notification rate. Age-stratified rates were calculated for pertussis and IPD.
Results: From early 2020, there was a substantial and sustained decrease in pertussis notifications in all jurisdictions. In 2021, for seven out of eight states and territories all-age pertussis notification rates were over 90% lower than the pre-pandemic period. In Victoria, pertussis notification rates were 84.6% lower (IRR, 0.15 [95% CI, 0.14–0.17]) than the prepandemic period. For IPD and IMD, the decrease in notification rates varied considerably between states and territories with Victoria, the state with the longest cumulative lock down period, having the most substantial decrease in 2021 (47.5% for IPD; IRR, 0.53 [95% CI, 0.45–0.61]) (81.4% for IMD; IRR, 0.19 [95% CI, 0.09–0.36]) and second highest decrease in 2020 (61.2% for IPD; IRR, 0.39 [95% CI, 0.33–0.46]) (68.0% for IMD; IRR, 0.32 [95% CI, 0.18–0.55]). Within jurisdictions significant decreases in IPD notifications were most observed among adults aged 25-69 years and 70 years and over than in younger age groups (0-4 years and 5-24 years).
Conclusion: This study has demonstrated the substantial decline in notification rates of three clinically significant conditions – pertussis, IPD, and IMD during time periods and in jurisdictions most impacted by COVID-19 NPIs. The degree and timing of decrease varied for each disease and between time periods and jurisdictions, suggesting differential impacts of lockdowns and border closures. As these public health measures are progressively lifted across Australia, disease rates should be monitored closely.
