TABLE 1—
New Seropositive Participants for SARS-CoV-2 as Determined by the Point-of-Care Test in the First and Second Pandemic Waves by General Characteristics: ENE–COVID, Spain, April 27–June 22 and November 16–30, 2020
| Characteristic | First Pandemic Wave | Second Pandemic Wave | ||||
| No. of Participantsa | Seropositivity,b % (95% CI) | Seropositivity Ratioc (95% CI) | No. of Participantsd | Seropositivity,e % (95% CI) | Seropositivity Ratioc (95% CI) | |
| Overall | 68 287 | 6.0 (5.7, 6.4) | 44 451 | 3.8 (3.5, 4.1) | ||
| Gender | ||||||
| Men | 32 742 | 5.9 (5.5, 6.4) | 0.98 (0.95, 1.02) | 20 956 | 3.7 (3.3, 4.1) | 0.98 (0.93, 1.04) |
| Women | 35 545 | 6.1 (5.8, 6.6) | 1.02 (0.98, 1.05) | 23 495 | 3.8 (3.5, 4.3) | 1.02 (0.97, 1.07) |
| Age, y | ||||||
| 0–19 | 12 581 | 4.0 (3.5, 4.5) | 0.66 (0.59, 0.74) | 7 543 | 4.0 (3.3, 4.8) | 1.06 (0.92, 1.21) |
| 20–34 | 9 552 | 5.1 (4.4, 5.8) | 0.84 (0.75, 0.95) | 5 217 | 4.3 (3.6, 5.1) | 1.14 (0.98, 1.32) |
| 35–49 | 16 051 | 6.4 (5.8, 7.0) | 1.05 (0.98, 1.14) | 10 427 | 3.6 (3.1, 4.2) | 0.96 (0.85, 1.07) |
| 50–64 | 16 799 | 7.2 (6.6, 7.8) | 1.19 (1.11, 1.28) | 11 806 | 4.0 (3.5, 4.6) | 1.05 (0.94, 1.18) |
| ≥ 65 | 13 304 | 7.3 (6.6, 8.0) | 1.21 (1.12, 1.31) | 9 458 | 3.2 (2.7, 3.8) | 0.86 (0.73, 1.00) |
| Nationality | ||||||
| Spanish | 65 173 | 6.0 (5.7, 6.4) | 1.00 (0.98, 1.01) | 43 084 | 3.7 (3.4, 4.0) | 0.98 (0.96, 0.99) |
| Other | 3 066 | 6.6 (5.3, 8.2) | 1.10 (0.89, 1.34) | 1 364 | 6.4 (4.7, 8.6) | 1.69 (1.26, 2.26) |
| Educationf | ||||||
| Less than primary | 3 680 | 6.4 (5.4, 7.6) | 0.98 (0.83, 1.15) | 2 464 | 3.7 (2.6, 5.1) | 0.98 (0.72, 1.34) |
| Primary | 7 813 | 6.5 (5.8, 7.4) | 0.99 (0.89, 1.11) | 5 429 | 3.5 (2.9, 4.4) | 0.95 (0.79, 1.14) |
| Secondary | 14 247 | 5.8 (5.2, 6.4) | 0.88 (0.81, 0.96) | 9 724 | 3.8 (3.3, 4.4) | 1.02 (0.90, 1.14) |
| High school | 11 292 | 7.0 (6.3, 7.7) | 1.06 (0.98, 1.15) | 7 338 | 4.4 (3.8, 5.2) | 1.19 (1.05, 1.35) |
| Vocational training | 6 369 | 5.9 (5.2, 6.7) | 0.90 (0.79, 1.02) | 4 413 | 3.4 (2.8, 4.1) | 0.90 (0.75, 1.09) |
| University | 12 593 | 7.4 (6.6, 8.2) | 1.12 (1.03, 1.22) | 8 379 | 3.4 (2.9, 4.0) | 0.91 (0.79, 1.05) |
| Occupationf | ||||||
| Active worker | 28 991 | 6.9 (6.5, 7.4) | 1.07 (1.03, 1.11) | 18 186 | 4.0 (3.6, 4.5) | 1.06 (0.99, 1.13) |
| Unemployed | 4 479 | 4.4 (3.6, 5.4) | 0.68 (0.56, 0.82) | 3 623 | 4.1 (3.3, 4.9) | 1.07 (0.89, 1.30) |
| Student | 4 230 | 4.8 (4.0, 5.8) | 0.75 (0.63, 0.88) | 2 243 | 4.5 (3.5, 5.8) | 1.19 (0.94, 1.49) |
| Retired | 13 239 | 7.3 (6.6, 8.0) | 1.12 (1.04, 1.21) | 9 859 | 3.1 (2.6, 3.7) | 0.82 (0.71, 0.95) |
| Sick leave | 1 480 | 5.5 (4.0, 7.3) | 0.84 (0.63, 1.13) | 1 163 | 2.9 (2.0, 4.3) | 0.78 (0.54, 1.12) |
| Homemaker | 3 682 | 5.3 (4.4, 6.3) | 0.81 (0.68, 0.96) | 2 464 | 3.9 (3.0, 5.2) | 1.04 (0.79, 1.36) |
| Other | 1 017 | 4.7 (3.3, 6.5) | 0.72 (0.52, 1.00) | 586 | 4.4 (2.5, 7.7) | 1.16 (0.66, 2.04) |
| Occupation sectorg | ||||||
| Telecommuting | 13 159 | 7.5 (6.9, 8.1) | 1.08 (1.02, 1.13) | 1 504 | 3.8 (2.8, 5.3) | 0.96 (0.71, 1.29) |
| Retail | 1 869 | 6.3 (4.9, 8.2) | 0.91 (0.72, 1.16) | 2 462 | 3.8 (2.9, 4.9) | 0.94 (0.74, 1.19) |
| Transport | 890 | 6.5 (4.6, 9.1) | 0.93 (0.67, 1.30) | 744 | 3.6 (2.2, 5.8) | 0.90 (0.57, 1.43) |
| Security | 710 | 6.9 (4.8, 9.8) | 0.99 (0.69, 1.41) | 487 | 5.5 (3.4, 8.8) | 1.38 (0.87, 2.19) |
| Cleaning | 902 | 5.4 (3.7, 7.7) | 0.77 (0.54, 1.10) | 838 | 4.9 (3.2, 7.5) | 1.22 (0.81, 1.86) |
| Health care | 1 300 | 11.1 (9.0, 13.6) | 1.60 (1.30, 1.95) | 990 | 6.1 (4.4, 8.5) | 1.52 (1.10, 2.10) |
| Nursing home | 1 148 | 10.2 (8.0, 12.8) | 1.46 (1.17, 1.82) | 831 | 3.6 (2.2, 5.8) | 0.90 (0.56, 1.43) |
| Home caregiver | 454 | 7.3 (4.4, 11.9) | 1.04 (0.64, 1.71) | 282 | 6.0 (3.4, 10.4) | 1.50 (0.85, 2.63) |
| Other | 8 457 | 5.2 (4.6, 5.9) | 0.75 (0.68, 0.84) | 10 043 | 3.8 (3.3, 4.3) | 0.94 (0.86, 1.03) |
| Smokerf | ||||||
| No | 41 881 | 7.2 (6.7, 7.6) | 1.11 (1.08, 1.13) | 27 660 | 4.1 (3.7, 4.5) | 1.08 (1.04, 1.12) |
| Yes | 15 885 | 4.7 (4.2, 5.2) | 0.72 (0.66, 0.79) | 10 391 | 3.0 (2.5, 3.5) | 0.78 (0.68, 0.98) |
| Body mass indexf | ||||||
| < 25 | 24 935 | 6.1 (5.6, 6.6) | 0.95 (0.90, 1.00) | 15 811 | 3.6 (3.2, 4.0) | 0.94 (0.87, 1.02) |
| 25–29 | 21 786 | 6.7 (6.2, 7.2) | 1.04 (0.99, 1.09) | 14 723 | 3.8 (3.4, 4.3) | 1.01 (0.93, 1.09) |
| ≥ 30 | 11 164 | 6.8 (6.1, 7.6) | 1.05 (0.96, 1.16) | 7 589 | 4.2 (3.6, 4.9) | 1.11 (0.99, 1.25) |
| No. chronic conditionsh | ||||||
| 0 | 21 054 | 6.9 (6.4, 7.4) | 0.97 (0.93, 1.02) | 14 093 | 3.6 (3.2, 4.1) | 1.02 (0.94, 1.10) |
| 1 | 10 338 | 6.7 (6.1, 7.5) | 0.96 (0.88, 1.04) | 7 348 | 3.6 (3.0, 4.2) | 1.00 (0.88, 1.15) |
| 2 | 6 060 | 8.2 (7.3, 9.2) | 1.16 (1.04, 1.30) | 4 290 | 3.4 (2.7, 4.1) | 0.94 (0.78, 1.13) |
| ≥ 3 | 4 318 | 7.1 (6.1, 8.2) | 1.01 (0.88, 1.15) | 3 201 | 3.6 (2.7, 4.7) | 0.99 (0.77, 1.28) |
| Chronic conditionh | ||||||
| Diabetes | 4 846 | 6.7 (5.8, 7.8) | 0.96 (0.84, 1.09) | 3 366 | 3.2 (2.5, 4.1) | 0.90 (0.72, 1.14) |
| Hypertension | 12 145 | 7.6 (6.9, 8.3) | 1.07 (1.00, 1.15) | 8 565 | 3.6 (3.0, 4.2) | 1.00 (0.88, 1.13) |
| CVD | 6 034 | 7.2 (6.3, 8.1) | 1.02 (0.91, 1.14) | 4 198 | 3.2 (2.5, 4.1) | 0.90 (0.72, 1.12) |
| Cancer | 1 958 | 7.8 (6.4, 9.5) | 1.11 (0.92, 1.34) | 1 344 | 2.6 (1.8, 3.9) | 0.73 (0.50, 1.07) |
| COPD | 3 378 | 7.1 (6.0, 8.2) | 1.00 (0.86, 1.16) | 2 309 | 3.5 (2.6, 4.6) | 0.97 (0.74, 1.27) |
| Asthma | 2 907 | 7.7 (6.5, 9.0) | 1.07 (0.91, 1.26) | 2 205 | 4.0 (3.0, 5.2) | 1.11 (0.86, 1.43) |
| Sleep apnea | 2 277 | 8.0 (6.6, 9.6) | 1.12 (0.94, 1.34) | 1 790 | 4.2 (3.1, 5.6) | 1.16 (0.89, 1.53) |
| CKD | 1 352 | 8.1 (6.4, 10.2) | 1.13 (0.90, 1.42) | 1 054 | 3.5 (2.3, 5.2) | 0.97 (0.65, 1.44) |
| IST | 1 208 | 7.5 (5.9, 9.6) | 1.05 (0.83, 1.33) | 952 | 3.9 (2.6, 6.0) | 1.10 (0.74, 1.64) |
| CLD | 510 | 6.2 (4.0, 9.6) | 0.86 (0.56, 1.31) | 475 | 2.8 (1.5, 5.4) | 0.80 (0.42, 1.49) |
| ACTD | 1 118 | 10.0 (7.8, 12.7) | 1.37 (1.08, 1.73) | 1 031 | 3.7 (2.2, 5.9) | 1.02 (0.63, 1.65) |
| Disability, % | ||||||
| No | 62 631 | 6.1 (5.8, 6.5) | 1.00 (0.99, 1.01) | 41 718 | 3.7 (3.4, 4.1) | 1.00 (0.99, 1.02) |
| < 33 | 583 | 5.4 (3.5, 8.1) | 0.87 (0.57, 1.33) | 416 | 3.0 (1.7, 5.2) | 0.79 (0.45, 1.40) |
| 33–65 | 1 779 | 6.3 (5.0, 7.9) | 1.03 (0.82, 1.28) | 1 250 | 3.8 (2.6, 5.5) | 1.01 (0.70, 1.46) |
| ≥ 66 | 946 | 5.9 (4.2, 8.2) | 0.96 (0.69, 1.33) | 650 | 3.9 (2.1, 7.3) | 1.05 (0.57, 1.92) |
| Household size, no. residents | ||||||
| 1 | 5 542 | 6.4 (5.6, 7.3) | 1.06 (0.94, 1.19) | 2 838 | 2.6 (2.0, 3.3) | 0.68 (0.52, 0.88) |
| 2 | 15 794 | 6.9 (6.3, 7.6) | 1.15 (1.06, 1.24) | 11 295 | 3.3 (2.8, 3.8) | 0.87 (0.75, 1.00) |
| 3–5 | 43 180 | 5.8 (5.4, 6.2) | 0.95 (0.92, 0.99) | 28 021 | 4.1 (3.7, 4.6) | 1.09 (1.04, 1.15) |
| ≥ 6 | 3 771 | 4.9 (3.8, 6.3) | 0.82 (0.64, 1.04) | 2 297 | 3.3 (2.3, 4.9) | 0.88 (0.60, 1.28) |
| Census tract income, percentile | ||||||
| < 5th | 3 267 | 5.8 (4.1, 8.2) | 0.96 (0.69, 1.36) | 1 957 | 5.4 (3.9, 7.4) | 1.43 (1.05, 1.95) |
| 5th–24th | 14 915 | 6.1 (5.3, 7.0) | 1.01 (0.88, 1.15) | 9 699 | 4.0 (3.2, 4.9) | 1.05 (0.88, 1.27) |
| 25th–49th | 17 261 | 5.9 (5.2, 6.8) | 0.98 (0.87, 1.12) | 11 173 | 3.7 (3.2, 4.4) | 0.99 (0.85, 1.15) |
| 50th–74th | 15 642 | 5.7 (5.0, 6.6) | 0.95 (0.84, 1.08) | 10 280 | 3.9 (3.3, 4.7) | 1.03 (0.89, 1.20) |
| 75–94th | 13 587 | 6.2 (5.4, 7.1) | 1.02 (0.90, 1.17) | 9 146 | 3.5 (2.8, 4.2) | 0.92 (0.77, 1.11) |
| ≥ 95th | 3 615 | 7.4 (5.8, 9.3) | 1.22 (0.96, 1.54) | 2 196 | 2.4 (1.6, 3.6) | 0.63 (0.42, 0.96) |
| Municipality size, no. inhabitants | ||||||
| < 5000 | 12 167 | 5.3 (4.6, 6.1) | 0.87 (0.76, 1.00) | 8 373 | 4.6 (3.7, 5.8) | 1.23 (0.99, 1.52) |
| 5000–19 999 | 14 439 | 4.7 (4.1, 5.3) | 0.77 (0.68, 0.87) | 9 565 | 3.4 (2.7, 4.3) | 0.90 (0.73, 1.11) |
| 20 000–99 999 | 20 652 | 4.9 (4.4, 5.4) | 0.81 (0.74, 0.89) | 13 189 | 3.4 (2.8, 4.0) | 0.90 (0.77, 1.04) |
| ≥ 100 000 | 21 029 | 7.7 (7.1, 8.4) | 1.28 (1.21, 1.35) | 13 324 | 4.0 (3.5, 4.6) | 1.05 (0.95, 1.17) |
Note. ACTD = autoimmune connective tissue disease; CI = confidence interval; CKD = chronic kidney disease; CLD = chronic liver disease; COPD = chronic obstructive pulmonary disease; CVD = cardiovascular disease; ENE–COVID = Spanish National Seroepidemiological Survey of SARS-CoV-2 Infection/Estudio Nacional de Sero-Epidemiología de la Infección por SARS-CoV-2 en España; IST = immunosuppressive therapy; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.
Participants who received the point-of-care test in at least 1 of the 3 rounds of the first survey phase.
Proportion of participants who had detectable immunoglobulin G antibodies against SARS-CoV-2 in any round of the first survey phase by the point-of-care test.
Seropositivity ratio with respect to all combined categories of a given characteristic.
Participants who tested negative by all received point-of-care tests during the first phase and underwent the test in the single round of the second survey phase.
Proportion of seronegative participants in the first phase who had detectable immunoglobulin G antibodies against SARS-CoV-2 in the single round of the second survey phase by the point-of-care test.
Among participants aged 17 y or older. Body mass index is defined as weight in kilograms divided by the square of height in meters.
Among active workers.
Among participants aged 40 y or older. Number of chronic conditions computed from those listed in the table.