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BACKGROUND AND OBJECTIVES: Childhood immunization may influence the development of asthma, possibly due to lack of infections or a shift in the T-helper cell type 1/T-helper cell type 2/regulatory T cells balance. We therefore investigated whether pertussis immunization in infancy is associated with asthma medication in adolescence. METHODS: After 14 years of no general pertussis vaccination, almost 82 000 Swedish children were immunized for pertussis in a vaccination trial between June 1, 1993, and June 30, 1994. In a follow-up analysis of almost 80 000 children, their data were compared with those of ~100 000 nonvaccinated children, born during a 5-month period before and a 7-month period after the vaccination trial. Data for the main outcome variable (ie, dispensed prescribed asthma medication for each individual in the cohort during 2008-2010) were obtained from the national prescription database. Multivariate regression models were used to calculate the effect size of vaccination on dispensed asthma medication (odds ratios [OR], 95% confidence intervals [Cl]). Approaches similar to intention-to-treat and per-protocol methods were used. RESULTS: The prevalence rates of various asthma medications for study patients at 15 years of age differed between 4.6% and 7.0%. The crude ORs for any asthma medication and antiinflammatory treatment in pertussis-vaccinated children after intention-to-treat analysis were 0.97 (95% Cl: 0.93-1.00) and 0.94 (95% Cl: 0.90-0.98), respectively. Corresponding adjusted ORs were 0.99 (95% Cl: 0.95-1.03) and 0.97 (95% Cl: 0.92-1.01). Similar ORs were found after per-protocol analysis. CONCLUSIONS: Pertussis immunization in infancy does not increase the risk of asthma medication use in adolescents. Our study presents evidence that pertussis immunization in early childhood can be considered safe with respect to long-term development of asthma. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Preterm birth is associated with respiratory morbidity later in life, including asthma. Previous studies have mainly focused on asthma in early childhood in children born extremely preterm. In this study, we examined the risk of asthma in a national cohort of schoolchildren grouped according to degree of immaturity expressed as completed gestational weeks at birth. METHODS: This was a register study in a Swedish national cohort of 1 100 826 children 6 to 19 years old. Retrieval of at least 1 prescription of inhaled corticosteroids (ICS) during 2006 was used as the main indicator for asthma. Logistic regression was used to test hypotheses, with adjustment for multiple socioeconomic and perinatal indicators. RESULTS: Degree of immaturity, expressed as completed gestational weeks at birth, had an inverse dose-response relationship with ICS use. Compared with children born between 39 and 41 weeks' gestation, the odds ratio for ICS use increased with the degree of prematurity, from 1.10 (95% confidence interval: 1.08-1.13) for children born in weeks 37 to 38, to 2.28 (95% confidence interval: 1.96-2.64) for children born in weeks 23 to 28, after adjustment for confounders The increase in ICS use with decreasing gestational age at delivery was similar in boys and girls, and declined with older age. CONCLUSION: Preterm birth increased the risk of ICS use in these 6-to 19-year-olds by degree of immaturity, from extremely preterm to early term birth. [ABSTRACT FROM AUTHOR]