Background: This study updates the COVID-19 pandemic surveillance in East Asia and the Pacific we first conducted in 2020 with two additional years of data for the region.
Objective: First, we measure whether there was an expansion or contraction of the pandemic in East Asia and the Pacific region when the World Health Organization (WHO) declared the end of the COVID-19 public health emergency of international concern on May 5, 2023. Second, we use dynamic and genomic surveillance methods to describe the dynamic history of the pandemic in the region and situate the window of the WHO declaration within the broader history. Third, we provide historical context for the course of the pandemic in East Asia and the Pacific.
Methods: In addition to updates of traditional surveillance data and dynamic panel estimates from the original study Post et al. (2021), this study used data on sequenced SARS-CoV-2 variants from the Global Initiative on Sharing All Influenza Data (GISAID) to identify the appearance and duration of variants of concern. We used Nextclade nomenclature to collect clade designations from sequences and Pangolin nomenclature for lineage designations of SARS-CoV-2. Finally, we conducted a one-sided t-test for whether regional weekly speed was greater than an outbreak threshold of ten. We ran the test iteratively with six months of data across the sample period.
Results: Several countries in the East Asia and Pacific region had COVID-19 transmission rates above an outbreak threshold at the point of the WHO declaration (Brunei, New Zealand, Australia, and South Korea). However, the regional transmission rate had remained below the outbreak threshold for four months. The rolling, six-month window t-test for regional outbreak status was trending toward statistical insignificance, with a P-value just under 0.10. From January 2022 onward, nearly every sequenced SARS-CoV-2 specimen in the region returned as the Omicron variant.
Conclusions: While COVID-19 continues to circulate in East Asia and the Pacific, transmission rates had fallen below outbreak status by the time of the WHO declaration. Compared to other global regions, East Asia and the Pacific had the latest outbreaks driven by the Omicron variant. COVID-19 appears to be endemic in the region, no longer reaching the threshold of the pandemic definition. However, the late outbreaks raise uncertainty about whether the pandemic was truly over for the region at the time of the WHO declaration.