Table 1. Seroprevalence of influenza A(H1N1)pdm09 virus antibody, England, 2010 and 2011*.
| Characteristic | No. seropositive samples/no. total samples† (% seropositive samples, 95% CI) |
|||||||
|---|---|---|---|---|---|---|---|---|
| Post–second wave‡ |
Pre–third |
Post–third wave |
||||||
| HI | MN | HI | MN | HI | MN | |||
| Age group, y | ||||||||
| <5 | 36/98 (0.37, 0.27–0.47) | 31/77 (0.4, 0.29–0.52) | 94/182 (0.52, 0.44–0.59) | 88/174 (0.51, 0.43–0.58) | 99/160 (0.62, 0.54–0.69) | 93/150 (0.62, 0.54–0.7) | ||
| 5–14 | 132/213 (0.62, 0.55–0.69) | 69/107 (0.64, 0.55–0.73) | 142/244 (0.58, 0.52–0.64) | 152/237 (0.64, 0.58–0.7) | 155/200 (0.78, 0.71–0.83) | 146/199 (0.73, 0.67–0.79) | ||
| 15–24 | 68/154 (0.44, 0.36–0.52) | 44/101 (0.44, 0.34–0.54) | 152/405 (0.38, 0.33–0.42) | 156/400 (0.39, 0.34–0.44) | 216/320 (0.68, 0.62–0.73) | 188/311 (0.6, 0.55–0.66) | ||
| 25–44 | 66/200 (0.33, 0.27–0.4) | 31/83 (0.37, 0.27–0.49) | 106/370 (0.29, 0.24–0.34) | 114/370 (0.31, 0.26–0.36) | 187/294 (0.64, 0.58–0.69) | 155/283 (0.55, 0.49–0.61) | ||
| 45–64 | 59/220 0.27, 0.21–0.33) | 42/110 (0.38, 0.29–0.48) | 69/320 (0.22, 0.17–0.26) | 93/318 (0.29, 0.24–0.35) | 62/138 (0.45, 0.36–0.54) | 52/135 (0.39, 0.3–0.47) | ||
| 65–74 | 36/145 (0.25, 0.18–0.33) | 27/87 (0.31, 0.22–0.42) | 35/168 (0.21, 0.15–0.28) | 42/167 (0.25, 0.19–0.32) | 38/74 (0.51, 0.39–0.63) | 38/74 (0.51, 0.39–0.63) | ||
| >75 | 55/172 (0.32, 0.25–0.4) | 77/163 (0.47, 0.39–0.55) | 16/93 (0.17, 0.1–0.26) | 25/92 (0.27, 0.18–0.37) | 46/71 (0.65, 0.53–0.76) | 39/71 (0.55, 0.43–0.67) | ||
| Region§ | ||||||||
| Total | 1,202 | 1,782 | 1,257 | |||||
| North West | 561 | 624 | 337 | |||||
| South West | 404 | 232 | 265 | |||||
| North East | 237 | 526 | 179 | |||||
| East | 0 | 292 | 122 | |||||
| Yorkshire and Humber | 0 | 108 | 354 | |||||
*HI, hemagglutination inhibition assay; MN, microneutralization assay. †Samples with titers >32 by HI or >40 by MN, ‡For data consistency, samples from only North West, South West, and North East regions were included in this analysis because these regions also were among the 5 regions in pre– and post–third wave samples. §Numbers by region describe total available number of samples (all analyzed at least by HI assay).