Table S3. A sensitivity analysis of GLMM-logit regression projecting uncertainties of the fixed-effects of age (years) and vaccination status induced by those contacts with multiple infectors.

Age and vaccination status	Susceptibility odds ratio*			Transmissibility odds ratio*
	Mean	(Quantiles, 0.025–0.975th)		Mean	(Quantiles, 0.025–0.975th)
Note: All children and adolescents (under 18 years) were unvaccinated, as they were not covered by the COVID-19 vaccination program in the Chinese mainland during the Delta outbreak. Vaccinated adults denote fully vaccinated adults, while partially vaccinated adults were deemed unvaccinated adults in the analysis. 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. * The GLMM-logit regression was repeated 1,000 times, where one single infector was randomly chosen for those contacts with multiple infectors in each stochastic realization. The mean odds ratio and 2.5–97.5th percentiles were summarized based on all results from 1,000 stochastic realizations. The odds ratios of age and vaccination status were adjusted by contact setting and the sex of the infector and contact.
Unvaccinated children (0–9 years)	2.13	(1.79, 2.57)		1.34	(0.52, 2.78)
Unvaccinated adolescents (10–17 years)	1.29	(1.04, 1.58)		0.72	(0.38, 1.19)
Unvaccinated adults (18–64 years)	Reference			Reference
Vaccinated adults (18–64 years)	0.47	(0.41, 0.52)		0.59	(0.35, 0.95)