Analysis of the influenza A (H1N1) 2009 pandemic infection in Japanese asthmatic patients: using a questionnaire-based survey.
BACKGROUND
Influenza infection is known to be an exacerbating factor in the control of asthma, therfore its prevention is critical in managing asthma. The aim of this study was to investigate the influenza A H1N1 2009 pandemic virus (H1N1 pdm09) infection in adult asthmatic patients.


METHODS
Data were obtained from a questionnaire-based survey of asthmatic patients conducted from September to October 2010 in Niigata Prefecture. Patient background, H1N1 pdm09 infection, vaccination status, and asthma exacerbation due to influenza infection were analyzed.


RESULTS
In total, 2,555 cases were analyzed. The incidence of the infection was 6.7% (95% confidence interval [CI]: 5.7-7.6), and the rate of vaccination was 63.9% (95% CI: 62.1-65.8). The odds ratio (OR) for vaccination against the infection among adult patients and younger patients (≤ the median age) were 0.61 (95% CI: 0.45-0.84) and 0.62 (95% CI: 0.42-0.90), respectively. However, OR among the older patient (> median age) were 1.38 (95%CI: 0.66-2.89). The rate of infection-induced asthma exacerbation was 23.2% (95% CI: 18.6-29.6), and the OR for vaccination against the infection-induced asthma exacerbation was 1.42 (95% CI: 0.69-2.92).


CONCLUSIONS
The effectiveness of the vaccination against the H1N1 pdm09 virus was confirmed during the first pandemic season, but it was limited. Further investigation on H1N1 pdm09 virus infection in asthmatics will be required.
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Nao
N
Koshio
Department of General Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan.
Takashi
T
Hasegawa
Department of Medicine, Prefectural Muikamachi Hospital, Niigata, Japan.
Kazuo
K
Suzuki
Division of Infection Control and Prevention, Niigata University Medical and Dental Hospital, Niigata, Japan.
Yoshinari
Y
Tanabe
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Toshiyuki
T
Koya
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Takuro
T
Sakagami
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Nobumasa
N
Aoki
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Yoshifumi
Y
Hoshino
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Hiroshi
H
Kagamu
Department of Respiratory Disease, Niigata Citizen Hospital, Niigata, Japan.
Hiroki
H
Tsukada
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Masaaki
M
Arakawa
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Fumitake
F
Gejyo
Division of Respiratory Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Ichiei
I
Narita
Department of General Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan.
Eiichi
E
Suzuki
D000328:Adult; D000368:Aged; D001249:Asthma / Q000150:complications*; D005260:Female; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology* / Q000517:prevention & control; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D062486:Public Health Surveillance; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014611:Vaccination