Table 4.

Odds Ratios for SARS-CoV-2 infection among 1,577 ill participants with and without evidence^† of prior SARS-CoV-2 infection by COVID-19 vaccination status^‡ and SARS-CoV-2 virus type.

	Prior infection	Total	No. SARS-CoV-2 positive	% positive	Unadjusted OR [95% CI]	Adjusted§ OR [95% CI]
Overall
Unvaccinated	No Prior infection	135	60	44	Referent
	Prior infection	154	45	29	0.52 [0.32, 0.84]	0.59 [0.32, 1.08]
2 doses	No Prior infection	389	129	33	Referent
	Prior infection	258	57	22	0.57 [0.40, 0.82]	0.47 [0.30, 0.76]
3 doses	No Prior infection	207	57	28	Referent
	Prior infection	434	107	25	0.86 [0.59, 1.25]	0.76 [0.49, 1.19]
Delta variant
Unvaccinated	No Prior infection	43	14	33	Referent
	Prior infection	37	5	14	0.32 [0.10, 1.0]	0.41 [0.11, 1.52]
2 doses	No Prior infection	189	20	11	Referent
	Prior infection	83	8	10	0.90 [0.38, 2.14]	0.84 [0.32, 2.22]
3 doses	No Prior infection	31	1	3	Referent
	Prior infection	33	1	3	0.75 [0.05, 12.48]	0.58 [0.03, 12.56]
Omicron variant
Unvaccinated	No Prior infection	74	38	51	Referent
	Prior infection	109	38	35	0.51 [0.40, 0.82]	0.86 [0.37, 2.01]
2 doses	No Prior infection	157	93	59	Referent
	Prior infection	158	47	30	0.29 [0.18, 0.46]	0.39 [0.22, 0.70]
3 doses	No Prior infection	162	53	33	Referent
	Prior infection	371	104	28	0.80 [0.54, 1.19]	0.81 [0.51, 1.29]

CI, confidence interval; OR, odds ratio

^†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.

^‡Vaccination status based on number of doses documented in electronic medical record received ≥14 days before illness onset for 2^nd dose or ≥7 days before illness onset for 3^rd dose.

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