Countries differ by size [1].

Because of this, total cumulative counts of most diseases at a country level will be spuriously correlated regardless of any actual association. “Population size” is a strong confounder, directly influencing total case numbers of all diseases.

It is thus not meaningful to observe that countries with 1 or more cases of cryptogenic paediatric hepatitis also had higher total counts of Omicron infection. [2] Those hepatitis cases, entirely unsurprisingly, occurred most commonly in larger countries, with double the population on average of countries with no cases.

Simply using per capita rates for Omicron rather than cumulative counts removes the difference in “burden” completely (22 cases per 100 in countries with hepatitis cases vs 19 cases per 100 in countries with no cases, p = 0.4).

This paper does not show any link between Omicron and this cryptogenic hepatitis.

This paper's conclusion should be rejected.

Conflict of interest

None

Funding Source

None

Ethics Approval

Not Required

Conflict of interest statement

Dr Kyle Sheldrick is the sole author.

He has a letter (as co-author) in relation to spurious correlation being used in anti-vaccination papers under consideration in another journal. He has no other relevant conflicts of interest.

[1] Personal experience.

[2] High population burden of Omicron variant (B.1.1.529) is associated with the emergence of severe hepatitis of unknown etiology in children, Nishiura, Hiroshi et al. International Journal of Infectious Diseases, no issue number, published ahead of print May 12, 2022

Article InfoPublication History

Accepted: July 5, 2022

Received: May 16, 2022

Publication stageIn Press Journal Pre-ProofFootnotes

Original article: High population burden of Omicron variant (B.1.1.529) is associated with the emergence of severe hepatitis of unknown etiology in children, Nishiura, Hiroshi et al. International Journal of Infectious Diseases, no issue number, published ahead of print May 12, 2022

Letter to the Editor: Failure to account for population size introduces spurious correlation for almost all diseases at a country level.

Identification

DOI: https://doi.org/10.1016/j.ijid.2022.07.020

Copyright

© 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.

User License Creative Commons Attribution (CC BY 4.0) | ScienceDirectAccess this article on ScienceDirect Related Articles