. 2024 Aug 28;12(10):e00691-24. doi: 10.1128/spectrum.00691-24

TABLE 2.

Estimated seroconversion rates by age and mask policy, September to December 2021

	Full mask (N = 3,849)			No mask (N = 1,365)			P value^b (permutation)
	Model estimated seroprevalence^c		Estimated population seroconversion^a	Model estimated seroprevalence		Estimated population seroconversion^a
	September	December	Estimated population seroconversion^a	September	December	Estimated population seroconversion^a
Overall	37.46%	48.76%	18.07%	44.03%	57.31%	23.73%	<0.001
5–11 years	41.15%	43.81%	4.51%	49.67%	52.87%	6.37%	0.002
12–17 years	40.14%	52.69%	20.97%	46.50%	61.05%	27.19%	<0.001

^{^a}

Estimated population seroconversion was calculated by formula (1). The proportion of seronegative children in September was calculated as one minus the seroprevalence.

^{^b}

Permutation test evaluated whether the difference of estimated population seroconversion between full and no mask groups is significant.

^{^c}

Robust Poisson regression was applied to estimate marginal means of seroprevalence by full and no mask groups in two time periods. The list of variables used in the model is described in Tables 4–6.