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Comparison of excess deaths and laboratory-confirmed COVID-19 deaths during a large Omicron epidemic in 2022 in Hong Kong

Background: Using a local elimination strategy, Hong Kong was able to minimize COVID-19 mortality in 2020 and 2021, but a large epidemic caused by the Omicron variant occurred in 2022. We aimed to estimate the overall, age-, sex-, epidemic period- and cause-specific excess mortality in 2022 in Hong Kong and compared excess mortality to laboratory-confirmed COVID-19 mortality. Methods: Negative binomial regression analysis was used to model time series of weekly all-cause and cause-specific deaths from 2010 to 2021 to predict the weekly number of deaths in 2022 against counterfactual baselines projected from the trends in the absence of a pandemic. The estimated excess deaths were compared with laboratory-confirmed COVID-19 deaths overall and by age and epidemic period. Results: We estimated that there were 13,500 (95% CI: 13,400-13,600) excess deaths in 2022, which was slightly higher than the 12,228 deaths recorded with laboratory-confirmed COVID-19, with the majority of the excess deaths and laboratory-confirmed deaths occurring among older adults. The increased number of excess deaths over laboratory-confirmed COVID-19 deaths was most substantial from February to April 2022 (a difference of 847 deaths), when the largest Omicron wave peaked. Most of the excess deaths (78%) were from respiratory causes, while 10% were from cardiovascular causes. A slight reduction in malignant neoplasm mortality was identified among older adults in 2022. Conclusions: A substantial increase in population mortality was identified in 2022 in Hong Kong, slightly larger than the laboratory-confirmed COVID-19 deaths. Apart from the possibility of underdiagnosis, excess deaths might also be attributed to the overload of healthcare resources during the pandemic. Deaths from COVID-19 may have displaced some deaths that would otherwise have occurred due to other causes although we did not find evidence of substantial mortality displacement.