Table 3. Secondary Attack Rates (SARs)^a of Child Care Providers, Students, and Household Surveillance Participants.

	Child care centers				Households
	Child care providers	Students	P value	Total	Adults	Childrenb	P value	Total
Total No. exposedc	409	1349	NA	1758	24	6	NA	30
Min-max cases (SAR, %)d	9-11 (2.2-2.7)	38-42 (2.8-3.1)	0	47-53 (2.7-3.0)	16 (67)	3 (50)	.64	19 (63)
No. exposed to adult cases	206	684	NA	890	7	3	NA	10
Min-max secondary cases due to adult contacts (SAR, %)d	4 (1.9)	14-16 (2.0-2.3)	1.0	18-20 (2.0-2.2)	3 (43)	1 (33)	1.0	4 (40)
No. exposed to child cases	203	665	NA	868	17	3	NA	20
Min-max secondary cases due to child contacts (SAR, %)d	5-7 (2.5-3.4)	24-26 (3.6-3.9)	.43	29-33 (3.3-3.8)	13 (77)	2 (67)	>.99	15 (75)

Abbreviations: Min-max, minimum to maximum; NA, not applicable.

^a Secondary attack rate is the number of new cases among contacts divided by the total number of contacts.

^b Includes household transmission of students and household child contacts.

^c Number of individuals exposed to child or adult isolated or index cases. Individuals were only counted once for an exposure to an index case; exposures to other secondary cases within the same classroom or household were not counted again.

^d Minimum definite cases and maximum cases, including possible cases that could not be determined with certainty because of multiple exposures or matching onset dates, including (1) cases meeting the definition of an index case but for which secondary cases all had an additional exposure outside of the classroom or household or (2) cases meeting the definition of a secondary case but with an exposure outside of the classroom or household.