Table 5. Pooled estimates of secondary attack rates, only high and moderate quality studies.

First Author	Number of Index Patients	Type of Contacts Traced in Study	Contacts		Secondary Attack Rate
			Number of Contacts Tested	Number of Contacts Testing Positive	(95% CI)†
Park, S.	4°	Household Contacts Only	11	0	0%
					(0% to 28.5%)
Park, S.	4°°	Household Contacts Only	4	0	0%
					(0% to 60.2%)
Ye, F.	1°	Close Contacts	44	4	9.1%
					(2.5% to 21.7%)
Huang, L.	1°	Close Contacts	22	7	31.8%
					(13.9% to 54.9%)
Li, P.	1°	Household Contacts Only	5	4	80%
					(28.4% to 99.5%)
Xiao, W.	2°	Household and Close Contacts	10	3	30%
					(6.7% to 65.2%)
Simple Pooled Estimate	13		96	18	18.8%*

Abbreviations: 95% CI, 95% confidence interval.

*Estimates have been simply pooled to facilitate interpretation of the body of evidence. Since studies are too heterogeneous in methods of contact tracing, confidence intervals on these estimates have not been calculated to not overstate any sense of precision.

°Index patients were pre-symptomatic (exposure occurred prior to symptom onset).

°°Index patients remained asymptomatic.

†Confidence intervals calculated for individual studies only, using the Clopper-Pearson exact method.