The Shift of Percent Excess Mortality during the COVID-19 pandemic (2020 – 2022) in Singapore, South Korea, Australia, New Zealand and Hong Kong SAR
Authors: Cao Xiaohan , Zi Yunlong , Zhu Yuyan 
Published: September 2022

Introduction

With the economic recession and pandemic fatigue, milder viral variants and higher vaccine coverage along the time lay the basis for lifting anti-COVID policies to restore COVID-19 normalcy. However, when and how to adjust the anti-COVID policies remain under debate in many countries.

Methods

In this study, four countries (Singapore, South Korea, Australia, and New Zealand) and one region (Hong Kong SAR), that have shifted from the zero-COVID (ZC) policy to or close to the living-with-COVID (LWC) during or after the Omicron outbreak, were selected as research objects. All-cause mortality data were collected for these objects from 2009-2019. The expected mortality was estimated by a simple linear regression method. Excess mortality over time was calculated as the difference between the expected mortality and the observed mortality. Finally, percent excess mortality (PEM) was calculated as the excess mortality divided by the expected mortality.

Results

In the examined four countries, PEM fluctuated around 0% and was lower than 10% most of the time under the ZC policy before 2022. After shifting to the LWC policy, all the examined countries increased the PEM. Briefly, countries with high population density (Singapore and South Korea) experienced an average PEM of 20-40% during the first half of 2022, and followed by a lower average PEM of 15-18% during the second half of 2022. For countries with low population density under the LWC policy, Australia experienced an average PEM of 39.85% during the first half of 2022, while New Zealand was the only country in our analysis that achieved no more than 10% in average PEM all the time. On the contrary, Hong Kong SAR under their ZC policy attained an average PEM of 71.14% during the first half of 2022, while its average PEM decreased to 9.19% in the second half of 2022 with LWC-like policy.

Conclusion

PEM under different policies within each country/region overtime demonstrated that the mortality burden caused by COVID-19 had been reduced overtime. Moreover, anti-COVID policies are suggested to control the excess mortality to achieve as low as 10% in PEM.

Contribution to the field

This study compared excess mortality within the same country/region, instead of among countries, thus, PEM during the outbreaks of different SARS-cov-2 variants overtime could reflect the effectiveness of regional specific anti-pandemic policies in protecting the lives of citizens locally.

Our analysis demonstrated that Singapore, South Korea and Australia might implement the LWC policy without sufficient preparation, which resulted in a very high mortality burden during the first half of 2022.

The reduced PEM in late 2022 in the examined countries/regions suggested that the mortality burden caused by COVID-19 was reduced overtime, laying a great foundation to call for a further relief of LWC policy in the world in the near future.

This study delineated a threshold of percent excess mortality, which is 10%, as a criterion to assess the effectiveness of anti-COVID policies.