Table 1. Age-specific seroprevalence and geometric means of hemagglutination inhibition titer to novel influenza A (H1N1) in Taiwan during the pre-pandemic (2007) and post-pandemic (2010) periods.
| Age, yrs | HI titers to 2009 pandemic influenza A (H1N1) | |||||
| 2007 (n = 1544) | 2010 (all subjects, n = 1558) | 2010 (unimmunized subjects, n = 912) | ||||
| GMT (95% CI) | % with titer ≥40 (95% CI) | GMT (95% CI) | % with titer ≥40 95% CI) | GMT (95% CI) | % with titer ≥40 (95% CI) | |
| <2 | 8.8 (7.4–10.3) | 0.0 (-) | 64.5 (20.7–108.3) | 24.2 (9.6–38.9) | 77.0 (14.7–139.2) | 17.4 (1.9–32.9) |
| 2–3 | 7.7 (6.4–9.0) | 0.0 (-) | 45.7 (21.3–70.1) | 22.6 (11.4–33.9) | 37.6 (18.7–56.6) | 23.5 (3.4–43.7) |
| 4–5 | 7.4 (6.1–8.8) | 0.0 (-) | 35.8 (30.3–41.3) | 32.1 (24.3–39.9) | 36.6 (27.6–45.5) | 28.4 (17.6–39.2) |
| 6–9 | 8.0 (6.8–9.2) | 0.0 (-) | 35.0 (28.8–41.2) | 42.9 (31.3–54.5) | 38.3 (24.2–52.3) | 47.8 (27.4–68.2) |
| 10–17 | 9.8 (8.6–11.0) | 1.33 (0–3.17) | 52.1 (42.1–62.1) | 55.4 (46.5–64.2) | 52.8 (32.6–73.0) | 47.7 (33.0–62.5) |
| 18–24 | 7.9 (6.9–8.8) | 0.63 (0–1.86) | 38.0 (28.5–47.5) | 29.7 (22.5–36.9) | 29.2 (24.8–33.6) | 22.2 (14.7–29.8) |
| 25–34 | 8.9 (7.2–10.6) | 1.03 (0–2.44) | 32.8 (28.8–36.8) | 32.9 (26.9–38.9) | 26.2 (23.3–29.1) | 18.9 (12.6–25.2) |
| 35–44 | 8.2 (6.5–9.9) | 0.51 (0–1.51) | 36.7 (29.5–43.9) | 33.0 (26.8–39.3) | 24.5 (22.8–26.3) | 20.1 (13.5–26.8) |
| 45–54 | 6.4 (5.8–7.0) | 0.50 (0–1.48) | 33.2 (26.4–40.0) | 24.9 (19.1–30.6) | 26.3 (21.3–25.9) | 14.6 (8.7–20.5) |
| 55–64 | 7.3 (6.3–8.3) | 1.90 (0–4.03) | 25.9 (23.8–28.0) | 20.2 (14.2–26.3) | 23.8 (21.8–25.9) | 15.4 (8.5–22.3) |
| ≥65 | 7.7 (6.8–8.5) | 1.79 (0.05–3.54) | 23.2 (21.0–25.4) | 14.1 (8.5–19.7) | 21.9 (20.5–23.4) | 11.8 (5.3–18.4) |
| Overall | 8.0 (7.6–8.4) | 0.91 (0.43–1.38) | 35.2 (32.8–37.6) | 29.9 (27.6–32.2) | 29.5 (27.1–31.8) | 20.6 (18.0–23.2) |
Abbreviations: GMT, geometric mean titer; CI, confidence interval