Children with a history of asthma may be at increased risk for breakthrough varicella infection, according to a new retrospective, population-based case-control study. The research also reaffirmed the benefit of the 2-dose varicella vaccine regimen for preventing breakthrough infection, and, in their conclusion, the investigators recommended adherence to the 2-dose varicella vaccine regimen for children with asthma.
The study was undertaken as a follow-up to an earlier investigation in which it was found that measles vaccine virus-specific immunoglobulin G levels waned more rapidly in children with asthma or who subsequently developed asthma compared with unaffected controls. Because there were no cases of measles among the prior study’s subjects, the question of whether a decline in vaccine-induced adaptive immune function increases the risk of clinical infection could not be explored. So, the researchers chose breakthrough varicella infection as a model for their case-control study to determine whether asthma is associated with an increased risk of vaccine-preventable disease.
The study included 165 children aged younger than 18 years with breakthrough varicella infection occurring between January 1, 2005, and December 31, 2011. These cases were identified from among residents of Olmsted County, Minnesota, based on the definition of having an illness with acute onset of generalized papulovesicular rash without other apparent cause more than 42 days after varicella vaccination. Each case was matched by age and sex with 2 controls.
Compared with controls, cases were more likely to have a history of asthma ever (35% vs 26% for controls; odds ratio [OR], 1.60; P=.033) and were less likely to have received 2 doses of the varicella vaccine (14% vs 24% for controls; OR, 0.29; P=.001). Lengthening of elapsed time since the first varicella vaccination also increased the risk of breakthrough infection.
In a multivariate model controlling for both number of varicella vaccine doses and elapsed time since the first varicella vaccination, a history of asthma remained a significant risk factor for breakthrough varicella (adjusted OR, 1.63; P=.032).
Whether or not asthma was controlled did not affect the risk of breakthrough varicella infection. Inhaled or systemic corticosteroid use in the 3 months prior to varicella vaccination was also not associated with breakthrough varicella infection risk. The researchers observed the latter findings are consistent with existing information that corticosteroids do not affect humoral or cell-mediated responses to vaccine. They noted, however, that the results may reflect small sample size, and they suggested further studies be conducted focusing on children with severe, steroid-dependent asthma.
Highlighting strengths of their study, the researchers listed its population-based design, the ability to capture all medical episodes to ascertain exposure and outcome status, and use of predetermined criteria for asthma and breakthrough varicella infection rather than International Classification of Diseases (ICD-9) codes or self-reports.
REFERENCES
- Umaretiya PJ, Swanson JB, Kwon HJ, Grose C, Lohse CM, Juhn YJ. Asthma and risk of breakthrough varicella infection in children. Allergy Asthma Proc. 2016;37(3):207-215.
- Yoo KH, Jacobson RM, Poland GA, et al. Asthma status and waning of measles antibody concentrations after measles immunization. Pediatr Infect Dis J. 2014;33(10):1016-1022.
