More H1N1 Seen in Children With Asthma

BY DOUG BRUNK
Elsevier Global Medical News

SAN FRANCISCO — During 2009’s peak influenza season, children with asthma were nearly twice as likely to be infected with the novel H1N1 influenza virus, compared with other viruses, according to results from a prospective single-center study.

In addition, H1N1 influenza infection caused increased severity of both cold and asthma symptoms, compared with other infections.

Although reasons for the association remain unclear, “this really proves that asthmatics need to be vaccinated for the flu, because we can see that they’re more susceptible to be infected when they’re exposed, and they’re more susceptible to have loss of asthma control when they get it,” lead investigator Dr. Kirsten M. Kloepfer said in an interview during a poster session at the annual meetingof the American Academy of Allergy, Asthma, and Immunology.

Dr. Kloepfer, a fellow in allergy and clinical immunology at the University of Wisconsin, Madison, and her associates evaluated 161 children aged 4-12 years who provided at least six of eight consecutive weekly nasal samples between Sept. 5 and Oct. 24, 2009. Of these 161 children, 94 had asthma and 67 did not. Their mean age was 9 years, and 60% were boys.

Dr. Kloepfer reported that the incidence of H1N1 influenza infection was 39% in asthmatics and 25% in nonasthmatics, a difference that was not statistically significant, with an odds ratio of 1.9 (P = .06).

However, after adjustment for race, sex, and allergic sensitization, the difference became statistically significant, increasing to an OR of 3.5 (P less than .002).

The incidence of human rhinovirus was statistically similar between the two groups (89% in asthmatics vs. 93% in nonasthmatics), as was the incidence of other viral infections (37% vs. 42%).

Both asthmatics and nonasthmatics reported significant increases in moderate and severe cold symptoms with H1N1, compared with rhinovirus (63% vs. 28%). Also, a significantly higher proportion of moderate to severe asthma was seen in H1N1 patients, compared with rhinovirus patients (48% vs. 23%). This association held true for severe asthma symptoms as well (19% vs. 4%). Dr. Kloepfer acknowledged certain limitations of the study, including its single-center design, the fact that it included only children aged 4-12 years, and the fact that it lasted only 8 weeks.

VITALS
Major Finding: During peak flu season, the incidence of H1N1 influenza infection was 39% among asthmatic children and 25% among their nonasthmatic counterparts (not statistically significant, odds ratio 1.9, P = .06). After adjustment for race, sex, and allergic sensitization, the difference became statistically significant (OR 3.5, P less than .002).
Data Source: Single-center study of 161 children aged 4-12 years.
Disclosures: The study was supported by grants from the National Institutes of Health. Dr. Kloepfer said she had no other relevant financial disclosures.