Table 5.
Secondary and clinical attack rates among COVID-19 cases identified through enhanced surveillance and contact tracing, NI, 26 February 2020 to 18 March 2020, n = 392
| Number of cases | Number of contacts | Proportion of contacts tested (%) | Attack rate (%) | Clinical attack rate (%) | |
|---|---|---|---|---|---|
| Risk category | |||||
| Household | 7 | 44 | 15.9 | 15.9 (6.6–30.1) | 15.9 (6.6–30.1) |
| High risk | 6 | 238 | 11.7 | 2.5 (0.9–5.4) | 1.7 (0.5–4.2) |
| Low risk | 0 | 110 | 3.6 | 0.0 | 0.0 |
| Age group (n = 259)a | |||||
| <5 | 0 | 8 | 0.0 | 0.0 | 0.0 |
| 5–10 | 0 | 5 | 0.0 | 0.0 | 0.0 |
| 10–20 | 1 | 12 | 16.7 | 8.3 (0.2–38.5) | 8.3 (0.2–38.5) |
| 20–30 | 4 | 57 | 19.3 | 7.0 (1.9–17.0) | 3.5 (0.4–12.1) |
| 30–40 | 4 | 55 | 10.9 | 7.3 (2.0–17.6) | 7.3 (2.0–17.6) |
| 40–50 | 2 | 50 | 12.0 | 4.0 (0.5–13.7) | 4.0 (0.5–13.7) |
| 50–60 | 1 | 30 | 6.7 | 3.3 (0.1–17.2) | 3.3 (0.1–17.2) |
| 60–70 | 0 | 26 | 3.8 | 0.0 | 0.0 |
| 70–80 | 1 | 10 | 10.0 | 10.0 (0.3–44.5) | 10.0 (0.3–44.5) |
| 80 + | 0 | 5 | 0.0 | 0.0 | 0.0 |
a
Age data not available for 135 (34.3%) contacts.