Table 3.
Age-specific seroprevalence and seroincidence in the Kathmandu Valley, Nepal, and Tamil Nadu, India, population-based serosurveys*
| Location and Age Group (Years) | N | n IgG Seropositive | % IgG Seroprevalence (95% CI) | Seroincidence per 1,000 Person-years (95% CI) | ||
|---|---|---|---|---|---|---|
| IgG Antibody Kinetics | IgG and IgM Antibody Kinetics | Derivative of Age-Dependent IgG Seroprevalence | ||||
| Tamil Nadu, India | ||||||
| 0–17 | 0 | 0 | – | – | – | – |
| 18–29 | 59 | 6 | 10.2% (2.4–17.9) | 10 (5–19) | 14 (8–22) | 4 (2–10) |
| 30–49 | 302 | 72 | 23.8% (19.0–28.7) | 15 (12–19) | 14 (11–17) | 7 (5–9) |
| 50–89 | 360 | 137 | 38.1% (33.0–43.1) | 29 (24–35) | 19 (16–23) | 8 (6–9) |
| Overall | 721 | 215 | 29.8% (26.5–33.2) | 20 (18–23) | 16 (14–18) | 7 (6–8) |
| Kathmandu Valley, Nepal | ||||||
| 0–17 | 876 | 1 | 0.1% (0–0.3) | 6 (4–9) | – | 0 (0–1) |
| 18–29 | 229 | 12 | 5.2% (2.3–8.1) | 14 (10–20) | – | 3 (1–4) |
| 30–49 | 0 | 0 | – | – | – | – |
| 50–89 | 0 | 0 | – | – | – | – |
| Overall | 1,105 | 13 | 1.2% (0.5–1.8) | 8 (7–11) | – | 1 (1–2) |
n () IgG seropositive = number of individuals in the population sample who were seropositive using the IgG mixture model cutoff of 1.8. IgG seroprevalence = the percentage of individuals who were seropositive divided by the total population in each stratum. Seroincidence using IgG antibody kinetics = the seroincidence rate per 1,000 person-years using longitudinal IgG antibody dynamics (method of Teunis and van Eijkeren30). Seroincidence using IgG and IgM antibody kinetics = the seroincidence rate per 1,000 person-years using longitudinal IgG and IgM antibody dynamics (method of Teunis and van Eijkeren30). Seroincidence using age-dependent IgG seroprevalence = seroincidence derived from the age-dependent cumulative hazard of IgG seroprevalence.