Table 5. Unadjusted and adjusted odds ratios for the effect of index case Alpha variant SARS-CoV-2 on household contact infection (defined as either anti-nucleocapsid IgG seropositivity or anti-spike IgG seropositivity in an unvaccinated individual) compared to non-VOC SARS-CoV-2.

	% infection (n/N)	Unadjusted OR (95% CI)	P-value	Adjusted OR*(95% CI)	P-value
Non-VOC	75% (77/102)
Alpha	87% (307/352)	3.1 (1.2–8.3)	0.02	2.1 (0.8–5.5)	0.14

All OR are adjusted for household level clustering

* adjusted for sex, age (years; linear), time between index PCR date and date of HHC serology (days; linear), duration of contact between infectious index and HHC (days; linear), IMD (rank; linear), intensity of contact (4 levels assuming a linear trend)

n = total positive, N = total population