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Volume 17, Number 9—September 2011

Research

Seroepidemiologic Study of Pandemic (H1N1) 2009 during Outbreak in Boarding School, England

Sandra Johnson, Chikwe IhekweazuComments to Author , Pia Hardelid, Nika Raphaely, Katja Hoschler, Alison Bermingham, Muhammad Abid, Richard Pebody, Graham Bickler, John Watson, and Éamonn O’Moore
Author affiliations: Author affiliations: Health Protection Agency, London, UK (S. Johnson, C. Ihekweazu, P. Hardelid, K. Hoschler, A. Bermingham, R. Pebody, G. Bickler, J. Watson); Health Protection Agency, Oxfordshire, UK (N. Raphaely, M. Abid, É. O’Moore)

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Table 1

Association of demographic characteristics, clinical illness, and interventions with study participants’ positive serologic test results during outbreak of pandemic (H1N1) 2009 at a boarding school, England*

Variable
No. participants
No. (%) with positive serologic test result
Odds ratio (95% CI)
Total 353 143 (40.5)
Demographics
Category
Students 216 123 (56.9) 7.74 (4.48–13.35)
Staff 137 20 (14.6) 1
Age group, y
13–15 90 46 (51.1) 1
16–18 126 77 (61.1) 1.50 (0.87–2.60)
20–49 71 12 (16.9) 0.19 (0.09–0.41)
>50 66 8 (12.1) 0.13 (0.06–0.31)
Sex, staff only†
F 71 5 (7.0) 1
M 66 15 (22.7) 3.88 (1.32–11.39)
Role, staff only‡
Nonteaching 93 6 (6.5) 1
Teaching 43 14 (32.6) 7.00 (2.46–19.90)
Clinical illness
ARI
No 199 62 (31.2) 1
Yes 141 77 (54.6) 2.66 (1.70–4.16)
ILI
No 277 95 (34.3) 1
Yes 63 44 (69.8) 4.44 (2.45–8.02)
Severity, n = 153§
Mild 81 38 (46.9) 1
Moderate and severe 59 39 (66.1) 2.21 (1.10–4.41)
Duration, d, n = 153§
1–2 14 6 (42.9) 1
3–6 52 27 (51.9) 1.44 (0.44–4.73)
7–10 18 12 (66.7) 2.67 (0.63–11.28)
>10
23
14 (60.9)
2.07 (0.54–8.00)
Interventions
Took antiviral drugs
No 96 48 (50) 1
Yes 207 68 (32.9) 0.49 (0.30–0.80)
Use of antiviral drugs: PEP vs. treatment dose
No antiviral drugs 96 48 (50.0)
PEP dose only 187 56 (30.0) 0.43 (0.26–0.71)
Treatment dose 20 12 (60) 1.5 (0.56–4.00)
Completion of PEP course of antiviral drugs¶
No antiviral drugs 96 48 (50.0) 1
Completed 25 9 (36.0) 0.56 (0.23–1.40)
Not completed 159 45 (28.3) 0.39 (0.23–0.67)
Seasonal influenza vaccine
No 105 29 (27.6) 1
Yes 230 106 (46.1) 2.24 (1.36–3.69)

*Categories in which the response was missing or unknown are shown in Table A1. CI, confidence interval; ARI, acute respiratory infection; ILI, influenza-like illness; PEP, postexposure prophylaxis.
†All students were male.
‡1 staff member was not included in the analysis because his occupation was unknown.
§Of those that self-reported ARI.
¶Excluding those who reported taking the treatment dose of antiviral drugs.

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