Table. Seroprevalence of SARS-CoV-2 antibodies in 3 surveys in Puducherry, India, 2020*.
| Variable | August 11–16, n = 869 |
September 10–16, n = 898 |
October 12–16, n = 900 |
|||||
|---|---|---|---|---|---|---|---|---|
| No, positive/ no. tested | % (95% CI) | No. positive/ no. tested | % (95% CI) | No. positive/ no. tested | % (95% CI) | |||
| Crude prevalence |
43/869 |
4.9 (3.5–6.4) |
|
186/898 |
20.7 (18.0–23.3) |
|
311/900 |
34.5 (31.5–37.7) |
| Age category, y | ||||||||
| 18–29 | 8/170 | 4.7 (1.5–7.8) | 33/165 | 20.0 (13.9–26.1) | 58/180 | 32.2 (25.8–39.3) | ||
| 30–44 | 13/295 | 4.4 (2.1–6.7) | 58/277 | 20.9 (16.2–25.7) | 92/252 | 36.5 (30.8–42.6) | ||
| 45–59 | 13/242 | 5.4 (2.5–8.2) | 64/271 | 23.6 (18.5–28.7) | 101/259 | 39.0 (33.2–45.0) | ||
|
>60 |
9/162 |
5.6 (2.0–9.1) |
|
31/185 |
16.7 (11.4–22.1) |
|
60/209 |
28.7 (23.0–35.1) |
| Sex | ||||||||
| M | 16/439 | 3.6 (1.9–5.4) | 95/443 | 21.4 (17.6–25.2) | 126/406 | 31.0 (26.7–35.6) | ||
| F |
27/428 |
6.3 (4.0–8.6) |
|
91/455 |
20.0 (16.3–23.6) |
|
183/491 |
37.2 (33.1–41.6) |
| Residence setting† | ||||||||
| Urban | 35/609 | 5.7 (3.9–7.5) | 130/629 | 20.7 (17.5–23.8) | 225/628 | 35.8 (32.1–39.7) | ||
| Rural |
8/260 |
3.1 (1.0–5.2) |
|
56/269 |
20.8 (16.0–25.7) |
|
86/272 |
31.6 (26.3–37.4) |
| Occupation‡ | ||||||||
| Healthcare workers | 2/29 | 6.9 (1.0–22.8) | 4/32 | 12.5 (1.0–24.0) | 18/66 | 27.2 (18.0–39.0) | ||
| Other frontline workers | 0/22 | 0 | 8/23 | 34.8 (15.3–54.2) | 6/15 | 40.0 (19.0–64.2) | ||
| Others |
41/818 |
5.0 (3.5–6.5) |
|
174/843 |
20.6 (17.9–23.4) |
|
287/819 |
35.0 (31.8–38.3) |
| Other characteristics | ||||||||
| COVID-19 | 4/34 | 11.8 (9.3–22.6) | 16/47 | 34.0 (20.5–47.6) | 82/184 | 44.5 (37.5–51.7) | ||
| COVID-19 diagnosis | 3/3 | 100 | 3/7 | 42.9 (6.1–79.5) | 25/29 | 86.2 (69.4–94.5) | ||
| COVID-19 symptoms in last 6 mo |
8/85 |
9.4 (3.2–15.6) |
|
10/44 |
22.7 (10.3–35.1) |
|
85/148 |
57.4 (49.3–65.1) |
| Cumulative case incidence (cumulative incidence ratio)§ |
2,987 (0.25%) |
|
12,331 (1.03%) |
|
23,080 (1.92%) |
|||
| Infection-to-case ratio¶ |
4.9%/0.25% = 19.6 |
|
20.9%/1.03% = 20.0 |
|
34.5%/1.92% = 18.0 |
|||
| Cumulative deaths |
43 |
|
187 |
|
441 |
|||
| Infection fatality ratio (cumulative deaths per 100,000 infected persons)# | 73.4 |
75.8 |
106.1 |
|||||
*COVID-19, coronavirus disease; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2. †Definitions used by the Office of the Registrar General & Census Commissioner, Government of India. ‡Other frontline workers included police officers, teachers, revenue officers, persons involved in COVID-19 response. §Calculated for data gathered until 2 weeks before the midpoint of the survey. ¶Infection-to-case ratio was calculated as crude seroprevalence / cumulative incidence ratio. #Infection-fatality ratio was calculated as cumulative deaths/crude prevalence × estimated population of the district.