Volume 27, Number 11—November 2021
Dispatch
Prevalence of SARS-CoV-2 Antibodies after First 6 Months of COVID-19 Pandemic, Portugal
Luísa Canto e Castro, Ana Helena Guia Pereira, Rita Ribeiro, Catarina Alves, Luís Veloso, Vera Vicente, Dalila Alves, Inês Domingues, Cláudia Silva, Andreia Gomes, Marta Serrano, Ângela Afonso, Marc Veldhoen, Maria José Rego de Sousa, José Germano Rego de Sousa, Germano de Sousa, Maria M. Mota, Bruno Silva-Santos1, and Ruy M. Ribeiro1
Table 2
Prevalence of antibodies against severe acute respiratory syndrome coronavirus 2, weighted and adjusted for the strata, by sociodemographic, health, and epidemiologic characteristics, Portugal, September 8‒October 14, 2020*
| Characteristic | No. participants | Seroprevalence, % (95% CI) |
|---|---|---|
| Overall |
13,398 |
2.2 (2.0–2.5) |
| Sex | ||
| M | 5,985 | 2.3 (2.0–2.8) |
| F |
7,413 |
2.1 (1.9–2.6) |
| Persons per household | ||
| 1 | 1,141 | 2.1 (1.6–4.6) |
| 2‒4 | 11,139 | 2.1 (1.9–2.5) |
| >5 |
1,069 |
2.3 (1.9–4.5) |
| Education | ||
| Less than high school | 4,145 | 2.1 (1.7–2.8) |
| High school, post-high school, no undergraduate degree | 3,373 | 2.0 (1.8–3.1) |
| Undergraduate or graduate degree | 5,603 | 2.1 (1.8–2.7) |
| Other |
270 |
2.9 (2.1–10.6) |
| Occupation | ||
| Employed | 7,584 | 2.3 (2.0–2.8) |
| Unemployed | 668 | 2.5 (1.9–5.1) |
| Student | 2,488 | 2.3 (1.9–3.5) |
| Retired | 1,943 | 1.6 (1.2–3.0) |
| Disability | 143 | 0.3 (0.2–3.0) |
| House worker | 223 | 1.0 (0.5–6.6) |
| Other |
333 |
3.8 (2.9–9.1) |
| Professional sector | ||
| Commerce/industry/building | 1,324 | 2.7 (2.2–4.3) |
| Administration/services | 1,930 | 2.5 (2.0–3.7) |
| Education | 1,351 | 1.5 (1.1–3.1) |
| Health | 875 | 3.2 (2.4–5.9) |
| Transportation | 207 | 3.2 (2.3–10.3) |
| Other |
1,772 |
1.8 (1.4–3.0) |
| For employed workers, current working arrangements | ||
| Teleworking | ||
| No | 6,480 | 2.4 (2.2–3.0) |
| Yes | 1,104 | 1.4 (1.0–3.1) |
| Physically at work, contact with colleagues | ||
| No | 263 | 2.8 (2.0–8.4) |
| Yes | 6,579 | 2.3 (2.1–2.9) |
| Physically at work, contact with the public | ||
| No | 4,184 | 2.3 (1.9–3.0) |
| Yes |
3,400 |
2.3 (2.0–3.2) |
| Body mass index, kg/m2† | ||
| Underweight and normal weight, <24.99 | 5,352 | 1.8 (1.5–2.3) |
| Overweight, 25.00–29.99 | 4,166 | 2.4 (2.0–3.1) |
| Obese, >30.00 |
1,766 |
2.5 (2.0–3.7) |
| Smoking status | ||
| Non-smoker | 9,235 | 2.4 (2.1–2.9) |
| Ex-smoker | 2,298 | 2.2 (1.8–3.4) |
| Smoker | 1,862 | 1.0 (0.9–2.2) |
| <20 cigarettes/day | 1,689 | 1.1 (0.9–2.4) |
| >20 cigarettes/day |
173 |
0.0 (0.0–5.2) |
| Physical exercise | ||
| No | 7,590 | 2.2 (2.0–2.7) |
| Yes |
5,808 |
2.0 (1.7–2.5) |
| BCG vaccine | ||
| No | 688 | 2.6 (2.0–5.2) |
| Yes | 10,672 | 2.2 (2.0–2.6) |
| Do not know |
2,038 |
2.0 (1.6–3.2) |
| Chronic disease | ||
| No | 9,681 | 2.2 (2.0–2.6) |
| Yes |
3,717 |
2.0 (1.6–2.8) |
| Were you in contact with someone infected? | ||
| No | 3,621 | 0.7 (0.6–1.3) |
| Yes | 1,025 | 16.2 (14.2–19.3) |
| Do not know |
8,752 |
1.2 (1.1–1.6) |
| Where was this potential contact? | ||
| Household | 295 | 23.6 (19.8–30.3) |
| Work | 432 | 9.6 (7.7–17.2) |
| Family outside household | 210 | 12.9 (10.2–20.9) |
| Healthcare institution | 48 | 7.5 (5.2–20.9) |
| Do not know |
40 |
18.4 (13.8–35.7) |
| Was someone in your household given a diagnosis of COVID-19? | ||
| No | 12,997 | 1.3 (1.2–1.6) |
| Yes |
401 |
28.3 (24.5–33.7) |
| Were you given a diagnosis of suspected COVID-19? | ||
| No | 12,729 | 1.1 (1.0–1.4) |
| Yes |
669 |
22.7 (19.9–26.8) |
| If you took a SARS-CoV-2 test, what was the result? | ||
| Positive | 136 | 80.1 (70.4–82.3) |
| Negative | 2,030 | 2.5 (2.1–4.0) |
| Inconclusive |
27 |
22.4 (15.4–37.1) |
| If you took an antibody test before, what was the result? | ||
| Positive | 31 | 62.1 (45.7–69.2) |
| Negative | 219 | 1.9 (1.4–11.1) |
| Inconclusive | 9 | 8.0 (4.6–18.8) |
*We include the number of participants in the study for reference purposes; these numbers are not adjusted for the population. BCG, Bacillus Calmette–Guérin; COVID-19, coronavirus disease; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2. †Calculated only for adults (>18 years of age).
1These authors were co-senior authors.
Page created: August 10, 2021
Page updated: October 19, 2021
Page reviewed: October 19, 2021
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