Volume 19, Number 11—November 2013
Dispatch
Incidence of Influenza A(H1N1)pdm09 Infection, United Kingdom, 2009–2011
Saranya Sridhar
, Shaima Begom, Alison Bermingham, Katja Hoschler, Walt Adamson, William Carman, Maria D. Van Kerkhove, and Ajit Lalvani
, Shaima Begom, Alison Bermingham, Katja Hoschler, Walt Adamson, William Carman, Maria D. Van Kerkhove, and Ajit Lalvani
Table 1
Seroprevalence of influenza A(H1N1)pdm09 antibodies at baseline, United Kingdom, 2009–2011*
| Risk factor | HI titer, no. (%)† |
GMT (95% CI) | p value§ | ||||
|---|---|---|---|---|---|---|---|
| <8 | 8–32 | >32 | Total | p value‡ | |||
| Total |
202 (62.0) |
39 (12.0) |
85 (26.1) |
326 |
11.6 (10.0–13.4) |
||
| Sex | |||||||
| M | 92 (58.2) | 22 (13.9) | 44 (27.8) | 158 | 0.48 | 12.8 (10.3–15.8) | 0.19 |
| F |
110 (65.5) |
17 (10.1) |
41 (24.4) |
168 |
10.6 (8.7–12.8) |
||
| Age group, y¶ | |||||||
| 18–25 | 57 (44.9) | 15 (11.8) | 55 (43.3) | 127 | Ref | 20.4 (15.5–26.8) | Ref |
| 26–40 | 99 (73.9) | 19 (14.2) | 16 (11.9) | 134 | <0.001 | 7.8 (6.6–9.1) | <0.001 |
| 41–55 | 32 (74.4) | 2 (4.7) | 9 (20.9) | 43 | 0.01 | 8.6 (6.2–11.8) | <0.001 |
| >56 |
9 (64.3) |
1 (7.1) |
4 (28.6) |
14 |
0.29 |
9.2 (5.3–16.0) |
0.14 |
| Seasonal influenza vaccination in 2008# | |||||||
| Yes | 23 (54.8) | 5 (11.9) | 14 (33.3) | 42 | 0.19 | 12.6 (8.6–18.3) | 0.56 |
| No |
174 (64.2) |
32 (11.8) |
65 (24.0) |
271 |
11.1 (9.5–13.0) |
||
| Self-reported history of ILI in 3 mo before recruitment** | |||||||
| Yes | 9 (36.0) | 3 (12.0) | 13 (52.0) | 25 | <0.01 | 35.7 (16.5–77.0) | <0.001 |
| No | 189 (64.3) | 36 (12.2) | 69 (23.5) | 294 | 10.5 (9.2–12.1) | ||
*HI, hemagglutination Inhibition; GMT, geometric mean titer; Ref, referent; ILI, influenza-like illness.
†Of the 342 participants in the study, 16 were missing data on HI assay results.
‡p value comparing the number of persons with a titer >32.
§p value comparing the GMT. For age categories, p value represents the test for trend.
¶Data available for 314 persons.
#Data available for 313 persons.
**Data available for 319 persons.
Page created: October 31, 2013
Page updated: October 31, 2013
Page reviewed: October 31, 2013
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