Data collection in pandemic times: the case of the Belgian COVID-19 health surveys

Table 2 Unweighted sample distribution of the surveys versus population distribution, COVID-19 health surveys, Belgium 2020-2022

	Survey 1 - Beginning of April 2020 (n=49334)	Survey 2 - End of April 2020 (n=42895)	Survey 3 - May 2020 (n=33913)	Survey 4 - September 2020 (n=30845)	Survey 5 - December 2020 (n=29855)	Survey 6 - March 2021 (n=20410)	Survey 7 - June 2021 (n=17774)	Survey 8 - October 2021 (n=17347)	Survey 9 - December 2021 (n=22354)	Survey 10 - March 2022 (n=13882)	Cohort (n = 12599)^a	Population distribution 2020^b,c
	%	%	%	%	%	%	%	%	%	%	%	%
Sex
Men	31.8	31.6	34.9	36.5	38.7	35.6	35.8	36.2	36.5	36.0	35.8	48.8
Women	68.2	68.4	65.1	63.5	61.3	64.4	64.2	62.8	63.5	64.0	64.1	51.2
Age group
18-24	5.3	3.3	3.3	2.3	2.5	1.7	3.3	5.8	4.6	2.8	1.0	10.1
25-34	19.7	15.7	14.2	12.4	11.9	9.8	10.6	9.3	10.3	7.9	8.5	16.2
35-44	24.4	22.6	20.3	20.4	19.3	17.9	16.6	15.5	18.4	14.1	16.4	16.2
45-54	21.2	22.9	21.1	21.9	20.9	20.8	20.0	19.5	20.6	19.6	20.5	17.0
55-64	18.1	21.4	23.0	23.7	24.6	24.4	24.7	24.3	23.3	25.4	26.1	16.6
65-74	9.5	11.9	15.6	16.5	17.9	21.2	20.6	21.0	19.2	24.2	23.0	12.7
75+	1.8	2.2	2.6	2.9	3.0	4.1	4.3	4.6	3.6	6.2	4.5	11.3
Highest diploma
Secondary diploma or less	27.6	26.8	25.2	25.3	24.4	24.8	25.5	27.7	27.5	26.1	25.3	58.9
Higher education	69.4	69.8	71.5	71.9	72.9	72.6	72.1	70.0	69.8	71.5	74.7	41.1
Region
Flemish Region	64.5	50.8	67.8	68.5	69.3	65.4	64.5	64.6	65.0	65.7	63.1	58.2
Brussels Capital Region	9.9	11.3	8.4	9.3	8.9	9.9	9.1	9.3	8.7	9.3	9.9	10.3
Walloon Region	25.7	37.9	23.8	22.2	21.8	24.7	26.4	26.0	26.3	25.0	26.7	31.6

^aCohort equals all participants who completed at least 5 surveys and provided consent to link their data collected in the different surveys
^bThe sex, age and regional distribution is based on the distribution of the Belgian registered population aged 18 and older on 01/01/2020, source Statistics Belgium [47]
^cThe education distribution is based on the distribution of the active and inactive population aged 20 till 64 according to the Labor Force Survey [48]

ISSN: 2049-3258