Increased risk of pertussis in patients with asthma.
BACKGROUND
The recent pertussis outbreak in California highlights the effect of pertussis on public health. In 2004, a pertussis outbreak occurred in Olmsted County, Minnesota, despite a high vaccine uptake. This outbreak provided a natural experiment to assess the relationship between asthma and pertussis.


OBJECTIVE
We sought to determine whether asthmatic subjects have a higher risk of pertussis than nonasthmatic subjects.


METHODS
We conducted a population-based case-control study. There were 223 pertussis cases identified by means of PCR in 2004 and 2005. We identified age- and sex-matched control subjects from 5537 patients with negative test results for pertussis. We conducted a comprehensive medical record review and applied predetermined criteria to ascertain asthma status. Conditional logistic regression was fit to assess the effect of asthma status on the risk of pertussis.


RESULTS
Of the 223 subjects, 164 were eligible for the study, and 328 matched control subjects (1:2 matching) were enrolled. Of these 164 subjects, 50% were male, and 82% were white. The median age at the index date of pertussis was 14 years. Sixty-two (38%) of the 164 cases had asthma before the index date of pertussis compared with 85 (26%) of the 328 control subjects (odds ratio, 1.73; 95% CI, 1.12-2.67; P = 013). The population attributable risk percentage of asthma for risk of pertussis was 17%.


CONCLUSIONS
Given the high prevalence of asthma and the ongoing risk of pertussis throughout the United States, consideration of defining asthmatic subjects as a target group for pertussis vaccination (eg, replacing decennial tetanus-diphtheria booster with tetanus, diphtheria, and acellular pertussis vaccine for adolescents and adults) should be given.
Mayo Medical School, Mayo Clinic, Rochester, MN, USA.
Conrad R
CR
Capili
Allison
A
Hettinger
Natalie
N
Rigelman-Hedberg
Lisa
L
Fink
Thomas
T
Boyce
Brian
B
Lahr
Young J
YJ
Juhn
D000293:Adolescent; D001249:Asthma / Q000150:complications*; D016022:Case-Control Studies; D002648:Child; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D012306:Risk; D014917:Whooping Cough / Q000150:complications* / Q000453:epidemiology*; D055815:Young Adult