Table 2. Anti-SARS-CoV-2 IgG antibody seroprevalence, Greece, April 2020 (n = 4,511).

April		Positive/ sample size	S1: Crude prevalence		S2: Age, sex and population-adjusted prevalence		S3: S2 + adjustment for sensitivity and specificity		S4: S3 + NPHO dataa
		n/N	Prevalence (%)	95% CI	Prevalence (%)	95% CI	Prevalence (%)	95% CI	Prevalence (%)	95% CI
Total		19/4,511	0.42	0.23–0.61	0.49	0.29–0.70	0.23	0–0.48	0.25	0.02–0.50
Age group (years)	0–29b	4/974	0.41	0.01–0.81	0.23	0–0.54	0	0–0.28	0.02	0.02–0.29
	30–49	2/1371	0.15	0–0.35	0.09	0–0.25	0	0–0.01	0.03	0.02–0.04
	50–69	5/1229	0.41	0.05–0.76	0.86	0.34–1.38	0.67	0.05–1.29	0.70	0.09–1.32
	≥ 70	8/937	0.85	0.26–1.44	1.26	0.55–1.98	1.15	0.30–2.00	1.17	0.32–2.02
Sex	Male	6/2,073	0.29	0.06–0.53	0.46	0.17–0.76	0.19	0–0.54	0.22	0.03–0.57
	Female	13/2,474	0.53	0.24–0.81	0.94	0.56–1.32	0.76	0.31–1.21	0.78	0.33–1.23
‘Ν-1’ chi-squared test Difference between sex			Difference = 0.24% p = 0.213		Difference = 0.48% p = 0.057		Difference = 0.57% p = 0.007		Difference = 0.56% p = 0.009
Large urban areas		9/997	0.90	0.32–1.49	0.99	0.38–1.61	0.83	0.09–1.56	0.85	0.11–1.58
Rest of country		10/3,514	0.28	0.11–0.46	0.27	0.10–0.45	0	0–0.18	0.01	0–0.19
‘Ν-1’ chi-squared test Difference between large urban areas and rest of country			Difference = 0.62% p = 0.007		Difference = 0.72% p = 0.021		Difference = 0.83% p < 0.001		Difference = 0.83% p < 0.001
CFR (%)		95% CI	IFR according to:
			S1		S2		S3		S4
			IFR (%)	95% CI	IFR (%)	95% CI	IFR (%)	95% CI	IFR (%)	95% CI
6.06		5.09–7.03	0.33	0.22–0.59	0.28	0.20–0.47	0.59	0.29–NA	0.54	0.27–6.85

CFR: case fatality rate; CI: confidence interval; IFR: infection fatality rate; NA: not applicable; NPHO: National Public Health Organisation.

^a NPHO data include all confirmed PCR-positive individuals.

^b A 12-year-old girl was detected positive for SARS-COV-2 IgG antibodies among 182 children aged 0–14; thus, the S4 is estimated to be 0.001% (95% CI: 0–0.09%) for the age group 0–14 years.