Table 5. Seroprevalence of IgG antibodies against SARS-CoV-2 among healthcare workers by vaccination status, June–July 2021.

Characteristic	Unvaccinated			Vaccinated with 1 dose			Vaccinated with 2 doses
	Number tested	Number positive (anti-N and/or anti-S1-RBD antibodies)	Cluster- and test-adjusted seroprevalence, percent (95% CI)	Number tested	Number positive (anti-N and/or anti-S1-RBD antibodies)	Cluster- and test-adjusted seroprevalence, percent (95% CI)	Number tested	Number positive (anti-N and/or anti-S1-RBD antibodies)	Cluster- and test-adjusted seroprevalence, percent (95% CI)
Age
18–44 years	651	429	65.6 (60.5–70.5)	828	712	88.2 (84.8–91.0)	3,654	3,260	90.1 (88.5–91.5)
45–60 years	105	77	73.8 (63.3–82.0)	142	120	85.1 (77.7–90.5)	1,750	1,489	86.1 (83.7–88.2)
>60 years	3	1	35.6 (3.8–87.4)	2	2	—	117	96	81.9 (73.2–88.2)
Gender
Male	343	230	66.0 (59.7–72.0)	451	392	88.3 (84.4–91.5)	2,729	2,402	88.7 (86.9–90.4)
Female	414	277	67.4 (61.4–72.9)	521	442	87.1 (83.0–90.4)	2,787	2,438	88.5 (86.7–90.3)
Other	2	0	—	—	—	—	5	5	—
Results of COVID-19 testing
Reported positive for COVID-19	140	116	85.0 (77.0–90.6)	154	146	95.6 (90.9–97.9)	1,060	1,013	96.3 (94.9–97.3)
Reported negative for COVID-19	267	156	58.7 (50.5–66.4)	491	408	85.9 (80.9–89.7)	2,637	2,225	85.4 (83.1–87.4)
Don’t know	16	11	71.9 (37.0–91.7)	15	15	—	112	104	92.1 (81.9–96.8)
Vaccine type
Covaxin	—	—	—	127	96	79.0 (69.5–86.0)	371	332	89.0 (84.8–92.2)
Covishield	—	—	—	841	734	88.5 (85.5–91.1)	5,132	4,495	88.6 (87.0–90.1)
Individuals with optimal interval between vaccination and blood sample collection (21 days or more after first dose, 7 days or more after second dose)
Covaxin	—	—	—	103	81	83.8 (73.5–90.6)	368	329	88.9 (84.7–92.1)
Covishield	—	—	—	675	599	91.0 (87.4–93.6)	5,127	4,490	88.6 (87.0–90.1)

N, nucleocapsid protein.