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The dates are part of the evidence

  1. 2015–2019

    School photoscreening took place in September.

  2. January–May 2020

    Home confinement changed school and household routines. Individual exposures were not fully measured.

  3. June 2020

    School photoscreening was conducted after confinement.

  4. 2021 publication

    Researchers reported a population pattern, with the strongest shift among ages 6–8.

Different screening months and several simultaneous changes matter when interpreting the comparison.

Feicheng, China: ten schools, ages 6–13. A before-and-after observation does not isolate a device, the virus or an individual household decision as the cause.Sources: [1] · Open or save this visual ↗

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