How common is long COVID? Why studies give different answers - Nature.com

Enormous databases do not necessarily allow scientists to solve long COVID mysteries, such as how well vaccination protects against the condition.

Health-care workers monitor a woman in a COVID-19 recovery gym in Genoa, Italy.Credit: Marco Di Lauro/Getty Clinical epidemiologist Ziyad Al-Aly has access to a treasure trove that many researchers … [+7598 chars]

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