Table 2.
Secondary attack rate (%) by selected characteristics among the contacts traced per COVID-19 primary case, Tamil Nadu, India, March–May 2020
| Selected characteristics | Number of contacts (%) | # COVID-19 positive | Secondary attack rate (%) (95% CI) | |
| Overall | 14 002 (100%) | 599 | 4 (4.0 to 4.6) | |
| Age in years (N=13 379) | ≤20 | 3203 (24%) | 138 | 4 (3.7 to 5.1) |
| 21–40 | 5511 (41%) | 237 | 4 (3.8 to 4.9) | |
| 41–59 | 3364 (25%) | 155 | 5 (4.0 to 5.4) | |
| 60+ | 1301 (10%) | 65 | 5 (4.0 to 6.4) | |
| Gender (N=13 969) | Male | 7443 (53%) | 280 | 4 (3.4 to 4.2) |
| Female | 6526 (47%) | 318 | 5 (4.4 to 5.4) | |
| Congregation exposure of primary case (N=14 002) | Yes | 3884 (28%) | 377 | 10 (8.8 to 10.7) |
| No | 10 118 (72%) | 222 | 2 (1.9 to 2.5) | |
| Contact type (N=14 002) | Household | 3474 (25%) | 464 | 13 (12.3 to 14.5) |
| Community | 10 417 (74%) | 135 | 1 (1.0 to 1.5) | |
| Healthcare personnel | 111 (1%) | 0 | 0 | |
| Symptom status of primary case (N=13 338) | Symptomatic | 607 (5%) | 37 | 6 (4.5 to 8.3) |
| Asymptomatic | 12 731 (95%) | 464 | 4 (3.3 to 4.0) | |