High population burden of Omicron variant (B.1.1.529) is associated with the emergence of severe hepatitis of unknown etiology in children.


Of the total of 39 countries, 12 detected at least one hepatitis case, and their confirmatory diagnoses of Omicron cases from 1 December 2021 to 27 April 2022 ranged from 4.4 to 11.9 million. Among the remaining 27 countries, the cumulative number ranged from 0.5 to 5.5 million cases. Countries with hepatitis cases experienced a higher population burden of Omicron cases (p=0.013).

Statistical association between the detection of at least one hepatitis case among children and the cumulative number of Omicron cases (B.1.1.529) was examined. Thirty-eight countries that belong to the Organization for Economic Cooperation and Development and Romania were included for the analysis.

Prior exposure to Omicron variant may be associated with an increased risk of severe hepatitis among children, indicating a critical need to conduct cofactor studies.

In industrialized countries that have experienced major extensive epidemics of Omicron (B.1.1.529), substantial fraction of the population was exposed including children.

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