Table S4. Estimating the association of potential risk factors with the risk of acquiring and transmitting the SARS-CoV-2 Delta variant based on 6,135 contacts in Hunan, China.

Characteristic	Multivariate analysis
	OR (95% CI)	P value
Note: All children and adolescents (under 18 years) were unvaccinated, as they were not covered by the COVID-19 vaccination program in mainland China during the Delta outbreak. Vaccinated adults denote fully vaccinated adults, while partially vaccinated adults were deemed unvaccinated adults in the analysis. Abbreviation: CI=confidence interval; OR=odds ratio. * P<0.05; ** P<0.01; *** P<0.001; † Contacts who were aged at or over 65 years or whose infectors were aged at or over 65 years were excluded from this analysis due to the small sample size. § For a contact who had interacted with more than one SARS-CoV-2 infection, we chose the first infected individuals they had been exposed to as the potential infector. If they had been exposed to multiple infectors at the same time, we randomly chose one from among these infectors as the potential infector.
Age (years) and vaccination status of contacts†
Unvaccinated children (0–9 years)	2.40 (1.12, 5.18)	0.025**
Unvaccinated adolescents (10–17 years)	1.38 (0.59, 3.25)	0.458
Unvaccinated adults (18–64 years)	Reference
Vaccinated adults (18–64 years)	0.54 (0.29, 0.99)	0.048*
Age (years) and vaccination status of infectors§
Unvaccinated children (0–9 years)	2.19 (0.52, 9.23)	0.285
Unvaccinated adolescents (10–17 years)	1.29 (0.31, 5.39)	0.728
Unvaccinated adults (18–64 years)	Reference
Vaccinated adults (18–64 years)	0.92 (0.32, 2.65)	0.875
Type of contact
Household contacts	6.90 (3.24, 14.68)	<0.001***
Health care	0.29 (0.06, 1.34)	0.113
Social contact	Reference
Workplace contact	0.58 (0.13, 2.50)	0.461
Other close contact	0.04 (0.01, 0.14)	<0.001***
General contact	0.10 (0.05, 0.21)	<0.001***
Sex of contacts
Female	Reference
Male	0.68 (0.41, 1.13)	0.138
Sex of infectors
Female	Reference
Male	0.42 (0.16, 1.10)	0.078