28914750

PMC5847407

Background

Live-attenuated influenza vaccines (LAIVs) are not licensed in children <2 years because of a wheezing safety signal that has not been fully elucidated. In 2000, the Kaiser Permanente Vaccine Study Center conducted a placebo controlled randomized clinical trial (RCT) of LAIV in children. As many of these children were still enrolled in Kaiser Permanente in 2014, we could assess the possible long-term association between LAIV and subsequent asthma diagnosis.

Methods

We identified all children who were originally enrolled into the LAIV RCT at < 3 years of age. We followed subjects until disenrollment from the health plan, a first diagnosis of asthma, or through the end of the study period in 2014. Asthma was defined by a first ICD-9-CM code (493.*) assigned at an outpatient or emergency department encounter. We performed a survival analysis of time to first asthma diagnosis among children receiving LAIV or placebo with a Cox proportional hazards model.

Results

We identified 1151 children in the original RCT who were aged 12 through 35 months at time of enrollment and who had received 2 doses of LAIV or placebo. A total of 767 (66.7%) RCT participants were still KPNC members in 2014. There was no evidence of differential drop-out by treatment group. The hazard ratio for new onset asthma for LAIV recipients compared to placebo was 1.1 (95% confidence interval 0.88–1.41, p=0.38).

Conclusions

We found no evidence of increased risk of subsequent asthma diagnosis among children < 3 years who received LAIV compared to placebo.

CDC Public Access

001/World Health Organization/International
U50 CK000431/CK/NCEZID CDC HHS/United States