Table 10.

Quality assessment using a modified Newcastle-Ottawa Scale for cross-sectional studies

Study ID	Selection bias		Performance bias			Detection bias			Attrition bias	Comparability
	Representativeness of sample	Percentage participation	Ascertainment of COVID-19	Confirmation of COVID-19	Blinding of assessors to prior exposure	Ascertainment of exposure to COVID-19	Confirmation of exposure to COVID-19	Blinding of assessors to COVID-19 status	Percentage in final analysis	Comparable in school	Comparable in age
Torres 2020 [23]	*	*	NR	NR	NR	*	NR	NR	NR	*	*
Armann 2020 [24]	*	NR	*	*	*	*	NR	*	NR	*	*
Desmet 2020 [25]	*	NR	*	NR	NR	NR	NR	NR	*	*	*
Fontanet 2020, High [11]	*	NR	*	*	*	*	NR	*	*	NR	NR
Fontanet 2020, Primary [12]	*	NR	*	NR	*	*	NR	*	*	NR	NR
Stein-Zamir 2020 [22]	*	*	*	NR	NR	*	NR	NR	*	*	*

* – denotes that the study met the criteria; NR – denotes either that the study did not meet criteria or that it was not reported