Table 3.

Contextual information on the nine largest (size ≥7) among 130 clusters emerging from overall 784 SARS-CoV-2-PCR positive index cases in educational institutions, Germany, August to December 2020

	Month of symptom onseta	Role of index	Age group of indexb	Type of institution	Number of high-risk contactsc		Number of secondary cases
					Total	% PCR-tested	Total	Children	Teachers
Cluster 1	December	Teacher	41–45	Day-care ≤ 6 years	43	Unknown	8	3	5
Cluster 2	October	Child	0–5	Day-care ≤ 6 years	150	70%	9	7	2
Cluster 3	December	Teacher	41–45	Day-care ≤ 6 years	45	Unknown	10	5	5
Cluster 4	November	Teacher	41–45	Day-care ≤ 6 years	79	86%	10	8	2
Cluster 5	October	Teacher	21–25	Day-care ≤ 6 years	87	85%	10	3	7
Cluster 6	November	Teacher	16–20	Day-care ≤ 6 years	37	Unknown	10	3	7
Cluster 7	October	Teacher	51–55	Day-care ≤ 6 years	106	95%	15	5	10
Cluster 8	October	Child	11–15	Secondary school	166	100%	7	7	0
Cluster 9	November	Teacher	46–50	Unknown	56	Unknown	7	0	7

^aDate of symptom onset for symptomatic cases, date of test for asymptomatic cases.

^bIn years.

^cHigh risk is defined as a person who stayed face to face (<1.5 m) for 15 min or longer, or in the same room for 30 min or longer with a COVID-19 case, respectively [20]. In crowded or unclear situations, or when resources do not allow for an individual risk assessment, particularly in the context of schools and day-care centres, all members of a class or group may be classified as high-risk contact persons [17].