Table 2. Seroincidence estimates of influenza A(H1N1)pdm09 virus antibody, England, 2010 and 2011.
| Age group, y | Change in antibody level, % (95% CI) |
||||
|---|---|---|---|---|---|
| Post–second wave to pre–third wave* |
Pre–third wave to post–third wave† |
||||
| Hemagglutination inhibition | Microneutralization | Hemagglutination inhibition | Microneutralization | ||
| <5 | 15 (3–27) | 10 (–3 to 24) | 10 (0–21) | 11 (1–22) | |
| 5–14 | –4 (–13 to 5) | 0 (–11 to 11) | 19 (11–28) | 9 (1–18) | |
| 15–24 | –7 (–16 to 3) | –5 (–15 to 6) | 30 (23–37) | 21 (14–29) | |
| 25–44 | –4 (–12 to 4) | –7 (–18 to 5) | 35 (28–42) | 24 (16–31) | |
| 45–64 | –5 (–13 to 2) | –9 (–19 to 1) | 23 (15–33) | 9 (0–19) | |
| 65–74 | –4 (–13 to 5) | –6 (–18 to 6) | 31 (18–43) | 26 (13–39) | |
| >75 | –15 (–25 to –4) | –20 (–32 to –8) | 48 (34–61) | 28 (13–42) | |
*Antibody levels at the end of the 2009–10 winter season compared with those before the 2010–11 season. †Antibody levels before and after the 2010–11 season.