Self-reported influenza vaccination and protective serum antibody titers in a cohort of COPD patients

BACKGROUND

COPD patients are advised vaccination against seasonal influenza, yet few studies have evaluated the protective antibody titers obtained in this patient group.

AIMS

1) To describe protective titers in COPD patients who self-reported influenza vaccination compared with vaccinated subjects without COPD and unvaccinated COPD patients, 2) analyze whether clinical parameters predicted influenza-specific antibody titers, and 3) whether antibody titers to influenza A at baseline could predict exacerbation risk or 5 years all-cause mortality.

METHODS

Influenza A (H1N1 and H3N2) titers were measured by haemagglutination inhibition assay in serum from 432 COPD patients and 77 controls in the Bergen COPD Cohort Study, at yearly visits between 2006/09. Titers of 40 or above were considered protective. We examined the variables sex, age, body composition, smoking, GOLD stage, yearly exacerbations, inhaled steroids, and Charlson score as predictive of titers, both univariately and in a multivariable model estimated by generalized estimating equations. The exacerbation incidence rate ratios and mortality hazard ratios were assessed by negative binominal and cox regression models respectively.

RESULTS

At baseline, 59% of COPD patients reported influenza vaccination during the last season. Levels of predictive titers varied considerably each season, but trended lower in COPD patients compared with controls. Neither sex, age, body composition, smoking, comorbidities, GOLD stage nor use of inhaled steroids consistently predicted titers. Having high titers at baseline did not impact later risk for exacerbations, but seemed to be associated with higher all-cause mortality, even after adjustment for COPD disease characteristics.

CONCLUSION

Vaccination coverage for influenza is imperfect for COPD patients in Norway, and there is a concern that immunization is suboptimal.

Quantitative computed tomography: emphysema and airway wall thickness by sex, age and smoking

We investigated how quantitative high-resolution computed tomography (HRCT) measures of emphysema and airway wall thickness (AWT) vary with sex, age and smoking history. We included 463 chronic obstructive pulmonary disease (COPD) cases and 431 controls. All included subjects were current or ex-smokers aged > or = 40 yrs, and all underwent spirometry and HRCT examination. The HRCT images were quantitatively assessed, providing indices on lung density and airway dimensions. The median (25-75th percentile) %LAA950 (% low-attenuation area < -950 HU) was 8.9 (3-19) and 4.7 (1-16) in male and female COPD cases, respectively, and 0.71 (0.3-1.6) and 0.32 (0.1-0.8) in male and female controls, respectively. %LAA950 was higher in ex-smokers and increased with increasing age and with increasing number of pack-years. The mean+/-SD standardised AWT was 0.504+/-0.030 and 0.474+/-0.031 in male and female COPD cases, respectively, and 0.488+/-0.028 and 0.463+/-0.025 in male and female controls, respectively. AWT decreased with increasing age in cases, and increased with the degree of current smoking in all subjects. We found significant differences in quantitative HRCT measures of emphysema and AWT between varying sex, age and smoking groups of both control and COPD subjects.