Table 2.

Secondary Household Attack Rates for West Coast Variants, Combined and Disaggregated by B.1.427 and B.1.429

			Unadjusted		Adjusted
	Positives Among Tested Contacts (%)	Mean Household Attack Rate (95% CI)	RR (95% CI)	P-value	aRR	P-value
Class
Non-West Coast	122/415 (29.4%)	25.6% (20.3–31)	…	…	…	…
West Coast	161/452 (35.6%)	35.9% (30.1–41.9)	1.28 (1.00–1.64)	.05	1.25 (.98–1.59)	.07
Lineage
B.1.427	78/235 (33.2%)	32.9% (25.4–40.6)	1.19 (0.89–1.59)	.20	1.19 (.90–1.59)	.20
B.1.429	79/196 (40.3%)	40.9% (31.5–50.5)	1.43 (1.07–1.91)	.02	1.36 (1.01–1.83)	.04

Relative risks estimated based on Poisson regression using generalized estimating equations and cluster-robust standard errors. Adjustment variables included age group, Latinx/Hispanic race, household size, and household density.

Abbreviations: aRR, adjusted risk ratio; CI, confidence interval; RR, risk ratio.