Hospitalizations Associated with Pandemic Influenza A (H1N1) 2009 in Asthmatic Children in Japan

ABSTRACT Background The pandemic influenza A (H1N1) 2009 [pdm (H1N1) 2009] spread through the world in 2009, producing a serious epidemic in Japan. Since it was suggested early that asthma is a risk factor for an increased severity of the infection, the Japanese Society of Pediatric Allergy and Clinical Immunology (JSPACI) organized a working group for countermeasures, and investigated asthmatic children admitted to the hospitals for pdm (H1N1) 2009 infection. Methods An appeal was made on the home page of the JSPACI to medical practitioners to input clinical information about asthmatic and non-asthmatic children (0–19 years) admitted to the hospital with pdm (H1N1) 2009 infection. Results A total of 862 children (390 with asthma, and 472 without asthma) from 61 medical centers were registered, and the data of 333 asthmatic children and 388 non-asthmatic children in all were entered in the analyses. The mean age was 7.4 ± 2.9 years in the asthma group and 6.9 ± 3.8 years in the non-asthma group. The percentage of children admitted for respiratory symptoms was significantly higher in the asthma group than in the non-asthma group (p Conclusions Asthma may not be a risk factor for severe pdm (H1N1) 2009 infection in children.