Table 3.

Seroprevalence of antibodies against SARS-CoV-2 Spike protein Receptor Binding Domain (RBD) by COVID-19 vaccination status and evidence of prior SARS-CoV-2 infection^†

	Total‡	No. (column %) Seropositive†	No. (column %) Seronegative	P-value§
Number of COVID-19 Vaccine Doses ¶				<0.01
Unvaccinated	267	172 (13)	95 (78)
2 doses	613	595 (45)	18 (15)
3 doses	561	552 (42)	9 (7)
Confirmed or possible prior SARS-CoV-2 infection ††				<0.01
Unvaccinated	148	138 (17)	10 (71)
2 doses	252	251 (31)	1 (7)
3 doses	429	426 (52)	3 (21)
No evidence of prior SARS-CoV-2 infection ‡‡				<0.01
Unvaccinated	119	34 (7)	85 (79)
2 doses	361	344 (68)	17 (16)
3 doses	132	126 (25)	6 (6)

RBD, SARS-CoV-2 protein receptor binding domain

^†Seropositive for SARS-CoV-2 Spike Protein RBD.

^‡Excludes 136 participants with indeterminate serostatus for RBD (n=7) or NP (n=129) antibody. 22 participants with indeterminate serostatus were unvaccinated, 34 received 2 doses of vaccine, and 80 received 3 doses of vaccine.

^§P-value for Chi-square test comparing proportion seropositive to seronegative.

^¶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.

^††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.

^‡‡Participants NP antibody seronegative without EHR-documented or self-reported positive COVID-19 test >90 days before onset of current illness