TABLE 4.

Odds ratios for SARS‐CoV‐2 infection among 1577 ill participants with and without evidence ^a of prior SARS‐CoV‐2 infection by COVID‐19 vaccination status ^b and SARS‐CoV‐2 virus type.

	Prior infection	Total	No. SARS‐CoV‐2 positive	% positive	Adjusted c OR [95% CI]
Overall
Unvaccinated	No Prior infection	135	60	44	Referent
	Prior infection	154	45	29	0.59 [0.32, 1.08]
2 doses	No Prior infection	389	129	33	Referent
	Prior infection	258	57	22	0.47 [0.30, 0.76]
3 doses	No Prior infection	207	57	28	Referent
	Prior infection	434	107	25	0.76 [0.49, 1.19]
Delta variant
Unvaccinated	No Prior infection	43	14	33	Referent
	Prior infection	37	5	14	0.41 [0.11, 1.52]
2 doses	No Prior infection	189	20	11	Referent
	Prior infection	83	8	10	0.84 [0.32, 2.22]
3 doses	No Prior infection	31	1	3	Referent
	Prior infection	33	1	3	NE d
Omicron variant
Unvaccinated	No Prior infection	74	38	51	Referent
	Prior infection	109	38	35	0.86 [0.37, 2.01]
2 doses	No Prior infection	157	93	59	Referent
	Prior infection	158	47	30	0.39 [0.22, 0.70]
3 doses	No Prior infection	162	53	33	Referent
	Prior infection	371	104	28	0.81 [0.51, 1.29]

Abbreviations: CI, confidence interval; NE, not estimates; OR, odds ratio.

^a Includes seropositive nucleocapsid protein (NP) antibody assay, electronic medical record documented positive SARS‐CoV‐2 molecular or antigen test, or participant self‐report of positive SARS‐CoV‐2 positive laboratory test >90 days before onset of current illness.

^b Vaccination status based on number of doses documented in electronic medical record received ≥14 days before illness onset for the second dose or ≥7 days before illness onset for the third dose.

^c Model adjusted for age, sex, race/ethnicity, site, illness onset week, self‐reported chronic medical condition, and high‐risk SARS‐CoV‐2 exposure.

^d Adjusted odds ratio not estimated due to too few cases.