Table 1.
Seroconversion and changes in SARS-CoV-2 anti-spike (anti-S) or anti-nucleocapsid (anti-N) immunoglobulin G (IgG) Gauteng Province during the Omicron wave in South Africa.
| Pre-BA.1-Dominant Wave Survey | Post-BA.1-Dominant Wave Survey | Individuals with Paired Samples from Pre-BA.1- and Post-BA.1-Dominant Wave Serosurveys and No COVID-19 Vaccination Following Pre-BA.1 Serosurvey 1 | |||||
|---|---|---|---|---|---|---|---|
| District | N | Seroprevalence 1 n (%; 95% CI 6) |
N | Seroprevalence 2 n (%; 95% CI 6) |
Seroconversion 3 n/N (%; 95% CI 6) |
Seroresponse for Anti-N and/or Anti-S IgG 4 n/N (%; 95% CI 6) |
Overall Serological Evidence SARS-CoV-2 Infection 5 n/N (%; 95% CI 6) |
| Gauteng Province | 7010 | 5124 (73.1; 72.0–74.1) | 7510 | 6823 (90.9; 90.2–91.5) | 382/510 (74.9; 71.0–78.5) |
933/1548 (60.3; 57.8–62.7) |
1315/2058 (63.9; 61.8–65.9) |
| Johannesburg District | 2468 | 1880 (76.2; 74.5–77.8) | 2630 | 2412 (91.7; 90.6–92.7) | 124/154 (80.5; 73.6–86.0) |
351/574 (61.1; 57.1–65.1) |
475/728 (65.2; 61.7–68.6) |
| Ekurhuleni District | 1861 | 1382 (74.3; 72.2–76.2) | 2132 | 1982 (93.0; 91.8–94.0) | 133/167 (79.6; 72.9–85.0) |
344/529 (65; 60.9–69.0) |
477/696 (68.5; 65.0–71.9) |
| Sedibeng District | 564 | 398 (70.6; 66.7–74.2) | 624 | 557 (89.3; 86.6–91.5) | 21/30 (70; 52.1–83.3) |
44/77 (57.1; 46.0–67.6) |
65/107 (60.7; 51.3–69.5) |
| City of Tshwane District | 1464 | 975 (66.6; 64.1–69.0) | 1455 | 1255 (86.3; 84.4–87.9) | 72/117 (61.5; 52.5–69.9) |
137/269 (50.9; 45.0–56.8) |
209/386 (54.1; 49.2–59.1) |
| West Rand | 653 | 489 (74.9; 71.4–78.1) | 669 | 617 (92.2; 89.9–94.0) | 32/42 (76.2; 61.5–86.5) |
57/99 (57.6; 47.7–66.8) |
89/141 (63.1; 54.9–70.6) |
| Age group stratification | |||||||
| <12 years | 753 | 423 (56.2; 52.6–59.7) | 584 | 491 (84.1; 80.9–86.8) | 53/74 (71.6; 60.5–80.6) |
82/126 (65.1; 56.4–72.8) |
135/200 (67.5; 60.7–73.6) |
| 12 to 17 years | 622 | 459 (73.8; 70.2–77.1) | 553 | 523 (94.6; 92.4–96.2) | 30/33 (90.9; 76.4–96.9) |
94/127 (74; 65.8–80.9) |
124/160 (77.5; 70.4–83.3) |
| 18 to 50 years | 4047 | 2978 (73.6; 72.2–74.9) | 4614 | 4204 (91.1; 90.3–91.9) | 210/270 (77.8; 72.4–82.3) |
495/836 (59.2; 55.8–62.5) |
705/1106 (63.7; 60.9–66.5) |
| >50 years | 1588 | 1264 (79.6; 77.5–81.5) | 1739 | 1587 (91.3; 89.8–92.5) | 85/128 (66.4; 57.9–74.0) |
256/450 (56.9; 52.3–61.4) |
341/578 (59; 54.9–62.9) |
n, number with outcome. N, denominator of population sampled. 1 Of the 2420 paired samples available, 2058 did not receive a COVID-19 vaccination between the pre- and post-Omicron BA.1 serosurveys. 2 Seroprevalence was defined as seropositive for anti-S or anti-N IgG irrespective of vaccination status. 3 Seroconversion is defined for individuals who were seronegative to both S and N on the pre-Omicron serosurvey and seroconverted to either S or N on the post-Omicron BA.1 serosurvey. 4 Seroresponse for anti-N and/or anti-S IgG is defined for individuals who were seropositive to either S or N on the pre-Omicron serosurvey and either seroconverted to S, seroconverted to N, or were seropositive to N on the pre-Omicron BA.1 serosurvey and had a ≥2-fold increase in anti-N titers on the post-BA.1-dominant wave serosurvey or were seropositive to S on the pre-BA.1 serosurvey and had a ≥2-fold increase in anti-S titers on the post-BA.1 serosurvey. 5 Overall serological evidence of SARS-CoV-2 infection in the period between the two surveys when the BA.1-dominant wave occurred was defined as either seroconversion or seroresponse for anti-N and/or anti-S IgG. 6 CI, confidence interval; confidence intervals have not been adjusted for multiplicity and should not be used for inference. The criteria used for determining seroconversion and seroresponse are outlined in Supplementary Table S2b.