For a study, researchers sought to test the hypothesis that COPD patients who did not acquire seroprotective levels following influenza vaccination were a less immune-competent group with a higher risk of morbidity and death. The COMIC cohort included 578 patients who had pre- and post-vaccination stable state blood samples where influenza-vaccine-specific antibodies were assessed. Titers of ≥40 after immunization were deemed protective and suggestive of immunocompetence. The primary outcome was death from any cause. Morbidity was measured by the period between the first severe acute exacerbation of COPD (severe AECOPD) and the first community-acquired pneumonia (CAP).

After immunization, 42% of the patients reached H1N1 and H3N2 seroprotective levels. Seroprotective levels against H3N2 were significantly greater (96%) than against H1N1 (43%). Having H1N1 and H3N2 seroprotective levels was not linked with decreased morbidity (severe AECOPD HR 0.91 (95% 0.66–1.25; P=0.564) (CAP HR 1.23 (95% 0.75–2.00; P=0.412)) or death (HR 1.10 (95% 0.87–1.38; P=0.433)).

Only a minority of patients in a large well-characterized COPD cohort developed seroprotective titers against H1N1 and H3N1 following annual influenza vaccination. While obtaining seroprotection following immunization might be regarded as a proxy sign of immunocompetence, it was not linked to decreased morbidity and death. Further research was needed to determine if it indicated that the immune state is not an important pheno/endotype in COPD patients for the course of their disease or that seroprotection is not an adequate (surrogate) marker to characterize immunological status in COPD.