Global, regional and national trends in incidence and mortality of pertussis from 1990 to 2021 and the comparison before and during COVID-19: a modelling analysis

Pertussis, a contagious respiratory disease, has seen a global decline in cases due to vaccination but has resurged because of waning immunity, with further impacts from the COVID-19 pandemic. This study aimed to assess the disease burden of pertussis worldwide from 1990 to 2021. Using the GBD 2021, we extracted age-standardized incidence rates (ASIR) and death rates (ASDR) of pertussis and analyzed the trends of them through calculating the estimated annual percentage change (EAPC) at global, regional and national levels from 1990 to 2021. Besides, we compared the EAPCs before and during the COVID-19 pandemic to explore the difference. Lastly, we investigated the association between age-standardized rates (ASR) and the socio-demographic index (SDI). From 1990-2021, the global ASIR and ASDR of pertussis witnessed an annual decline of 2.57 % (95 %CI: 1.91-3.22 %) and 3.20 % (2.54-3.85 %) on average, respectively. During the COVID-19 pandemic, the ASR showed steep downward trends not only globally but also in diverse regions. Nevertheless, before the pandemic, Southern Sub-Sahara Africa witnessed upward trends in ASR, whose EAPCs were 0.85 % (0.67-1.02 %) for ASIR and 0.65 % (0.41-0.88 %) for ASDR. Additionally, a remarkable negative correlation was revealed between ASR and SDI (Regional level: r = -0.843; r = -0.885. National level: r = -0.621; r = -0.762. All P < 0.001.), corroborating with the observation that regions and countries with lower SDI bore the higher disease burden. From 1990-2021, global burden of pertussis showed a downward trend, with significant drops during the COVID-19 pandemic. However, before the COVID-19, Southern Sub-Saharan Africa saw rising ASIR and ASDR, contrary to the majority. Besides, SDI was proved negatively correlated with ASR, indicating that low-SDI countries, especially in Sub-Saharan Africa, faced high disease burden, which highlighted the need for improving immunization, surveillance, and healthcare resource allocation to control pertussis effectively.