Abstract
BACKGROUND: Asthmatics have increased risks of common and serious microbial infections including vaccine preventable diseases. Little is known about whether asthma influences waning of humoral immunity. We assessed whether asthma status influences waning of anti-measles virus antibody concentrations over time. METHODS: The study used a cross-sectional study cohort of healthy children who had been immunized with 1 dose of MMR-II at age approximately 15 months. Between 5 and 12 years of age, measles vaccine virus-specific antibody (IgG) values were measured by enzyme immunoassay and considered seropositive if the enzyme immunoassay index unit was ≥ 1. The medical records were reviewed to determine asthma status during the first 18 years of life by applying predetermined criteria for asthma. A least squares regression model was used to evaluate the effect of asthma status on the relationship between measles antibody titer and time elapsed between the initial measles vaccination and measurement of measles antibody concentrations. RESULTS: Of the 838 eligible children, 281 (34%) met criteria for asthma. Measles antibody waned over time (r = -0.19, P < 0.001), specifically more rapidly in asthmatics (r = -0.30, P < 0.001, a decrease of -0.114 unit per year) than non-asthmatics (r = -0.13, P = 0.002, a decrease of -0.046 unit per year; P value for interaction = 0.010). This differential waning rate resulted in a lower mean (SD) measles antibody concentration [1.42 (0.67) vs. 1.67 (0.69), P = 0.008] and lower seropositivity rate (73% vs. 84%, P = 0.038) in asthmatics than non-asthmatics starting around 9.3 years after the initial measles vaccination. CONCLUSION: Asthma status is associated with waning kinetics of measles antibody among children.