Asthma and Risk of Breakthrough Varicella Infection in Children.

Background:We recently reported a more rapid waning of vaccine-induced humoral immunity (measles vaccine) in children with asthma.It is unknown if asthma affects susceptibility to vaccine-preventable diseases.Objective: To determine whether asthma is associated with an increased risk of vaccine-preventable disease, e.g., breakthrough varicella infection.Methods: This was a retrospective population-based case-control study that examined cases of breakthrough varicella among children between 2005 and 2011.Children with a diagnosis of breakthrough varicella infection in Olmsted County, Minnesota (infection of Ͼ42 days after vaccination) between 2005 and 2011 and two age-and sex-matched controls were enrolled for each case.Asthma status was determined by using predetermined criteria.Conditional logistic regression models were used to calculate matched odds ratios (OR) and their corresponding 95% confidence intervals (CI).Results: Of the 165 cases and their 330 matched controls, 48% were boys and the mean (standard deviation) age at the index date was 6.6 Ϯ 3.5 years for both cases and controls.Of the 330 controls, 80 (24%) had two doses of the varicella vaccine compared with only 23 (14%) of the 165 cases (OR 0.29 [95% CI, 0.14 -0.61]; p ϭ 0.001).Children with a history of asthma ever had a higher risk of developing breakthrough varicella compared with those without a history of asthma (adjusted OR 1.63 [95% CI, 1.04 -2.55]; p ϭ 0.032) when adjusting for elapsed time since the first varicella vaccination and the number of varicella vaccine doses.Conclusions: A history of asthma might be an unrecognized risk factor for breakthrough varicella infection.Children with asthma should follow the two-dose varicella vaccine policy.