Volume 29, Number 3—March 2023
Dispatch
Seroprevalence of Specific SARS-CoV-2 Antibodies during Omicron BA.5 Wave, Portugal, April–June 2022
Irina Kislaya
, Aryse Melo, Marta Barreto, Camila Henriques, Carlos Aniceto, Carla Manita, Sara Ramalhete, João Almeida Santos, Sofia Soeiro, Ana Paula Rodrigues, and ISN4COVID-19 Group1
, Aryse Melo, Marta Barreto, Camila Henriques, Carlos Aniceto, Carla Manita, Sara Ramalhete, João Almeida Santos, Sofia Soeiro, Ana Paula Rodrigues, and ISN4COVID-19 Group1
Table 1
Seroprevalence of specific SARS-CoV-2 antibodies, stratified by sex, age group, and region of residence, Portugal, April 27–June 8, 2022*
| Characteristic | N IgG positive, % (95% CI) | S IgG positive, % (95% CI) | N or S IgG positive, % (95% CI) |
|---|---|---|---|
| Overall |
27.3 (25.5–29.1) |
95.0 (94.2–95.7) |
95.8 (95.0–96.4) |
| Sex | p = 0.8789 | p = 0.9801 | p = 0.8544 |
| M | 27.4 (25.0–30.0) | 95.0 (93.9–95.9) | 95.7 (94.6–96.6) |
| F |
27.1 (24.7–29.7) |
95.1 (93.7–96.1) |
95.8 (94.6–96.8) |
| Age group, y | p<0.001 | p<0.001 | p<0.001 |
| 0–4 | 39.2 (32.3–46.5) | 71.2 (64.4–77.2) | 76.2 (69.6–81.7) |
| 5–9 | 32.9 (26.6–39.9) | 78.2 (71.5–83.6) | 78.7 (72.1–84.1) |
| 10–19 | 40.0 (35.0–45.2) | 95.2 (92.5–97.0) | 96.2 (93.7–97.7) |
| 20–29 | 29.7 (24.8–35.2) | 97.9 (95.7–99.0) | 98.6 (96.5–99.5) |
| 30–39 | 30.3 (25.2–36.0) | 96.3 (93.4–98.0) | 96.9 (94.1–98.4) |
| 40–49 | 27.2 (22.3–32.7) | 96.6 (93.8–98.2) | 97.7 (95.3–98.9) |
| 50–59 | 27.0 (22.2–32.4) | 97.5 (95.0–98.8) | 97.7 (95.1–98.9) |
| 60–69 | 21.0 (16.7–26.0) | 97.0 (94.4–98.4) | 97.4 (94.8–98.7) |
| >70 |
17.3 (13.5–21.7) |
96.7 (94.2–98.2) |
97.2 (94.8–98.6) |
| Region of residence | p = 0.1465 | p = 0.0141 | p = 0.0315 |
| Norte | 24.8 (21.6–28.3) | 96.4 (94.9–97.5) | 96.8 (95.3–97.8) |
| Centro | 28.2 (24.3–32.6) | 95.2 (93.0–96.7) | 95.9 (93.8–97.3) |
| Lisboa e Vale do Tejo | 29.3 (26.3–32.6) | 94.2 (92.5–95.6) | 95.3 (93.7–96.5) |
| Alentejo | 25.4 (21.7–29.5) | 95.3 (93.1–96.9) | 96.0 (93.9–97.3) |
| Algarve | 27.6 (23.2–32.5) | 91.0 (87.6–93.5) | 91.7 (88.4–94.1) |
| Madeira | 31.0 (26.8–35.5) | 94.1 (92.0–95.7) | 95.6 (93.7–97.0) |
| Açores | 24.4 (20.6–28.6) | 93.7 (91.1–95.6) | 95.9 (93.8–97.3) |
*ISN4COVID-19 study. Weighted to match the distribution of the resident population of Portugal (Census 2021) by sex, age group, and region. p values indicate design-adjusted χ2 testing used to compare seroprevalence by sex, age group, and region. N, nucleocapsid protein; S, spike protein.
1Group members are listed at the end of this article.
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