Table 1.
Comparison of Infections Defined Using Conventional and Modified Interpretations of Paired Sera Among Participants in a Longitudinal Cohort Study Conducted in Pau da Lima, Salvador, Brazil, 2013–2015
| Interval | CompleteFollow-ups | Conventional Interpretation | Accounting for Titer Decay a | ||||
|---|---|---|---|---|---|---|---|
| SC | FFT | Infection Rate b | SC Median (IQR) | FFT Median (IQR) | Infection Rate b Median (IQR) | ||
| 6 months | |||||||
| Period 1 | 1,593 | 48 | 16 | 40.2 | 58 (57, 60) | 14 (13, 15) | 45.8 (45.2, 46.5) |
| Period 2 | 1,485 | 87 | 9 | 64.6 | 99 (98, 101) | 7 (6, 8) | 71.4 (70.7, 72.7) |
| Period 3 | 1,601 | 36 | 11 | 29.4 | 43 (42, 44) | 21 (20, 22) | 40.0 (39.4, 40.6) |
| Period 4 | 1,399 | 52 | 14 | 47.2 | 68 (66, 70) | 19 (17, 20) | 62.2 (60.8, 62.9) |
| 12 months | |||||||
| Year 1c | 1,444 | 69 | 3 | 49.9 | 109 (107, 110) | 11 (10, 11) | 82.4 (81.7, 83.1) |
| Year 2d | 1,292 | 36 | 5 | 31.7 | 64 (61, 67) | 20 (20, 21) | 65.8 (63.5, 67.3) |
Abbreviations: IQR, interquartile range; FFT, 4-fold titer rise; SC, seroconversion.
a The values for the interpretation allowing for titer decay are based on 10,000 imputations using a decay rate sampled from its distribution.
b Per 1,000 population.
c Periods 1 and 2.
d Periods 3 and 4.