Table 5.

Adjusted^† vaccine effectiveness against COVID-19 by SARS-CoV-2 variant stratified by prior infection status^‡

	Vaccination§	Total	SARS-CoV-2 positive	% positive	Unadjusted VE [95% CI]	Adjusted† VE [95% CI]
Overall
No prior infection	Unvaccinated	135	60	44	Referent
	2 doses	389	129	33	38 [8, 58]	17 [−40, 51]
	3 doses	207	57	28	53 [25, 70]	53 [10, 76]
With prior infection	Unvaccinated	154	45	29	Referent
	2 doses	258	57	22	31 [−8, 56]	42 [−1, 66]
	3 doses	434	107	25	21 [−19, 47]	55 [21, 74]
Delta variant
No prior infection	Unvaccinated	43	14	33	Referent
	2 doses	189	20	11	76 [46, 89]	70 [11, 90]
	3 doses	31	1	3	93 [44, 99]	97 [60, 100]
With prior infection	Unvaccinated	37	5	14	Referent
	2 doses	83	8	10	32 [−125, 79]	23 [−225, 82]
	3 doses	33	1	3	84 [−44, 98]	87 [−86, 99]
Omicron variant
No prior infection	Unvaccinated	74	38	51	Referent
	2 doses	157	93	59	−38 [−140, 21]	−53 [−205, 23]
	3 doses	162	53	33	54 [19, 74]	23 [−72, 65]
With prior infection	Unvaccinated	109	38	35	Referent
	2 doses	158	47	30	21 [−33, 53]	45 [−4, 70]
	3 doses	371	104	28	27 [−15, 54]	57 [20, 76]

CI, confidence interval; VE, vaccine effectiveness

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

^‡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.