Purpose: Vaccines have been shown to induce a transient impairment of endothelial function and arterial elastic properties. Newly developed vaccines against the pandemic influenza A/H1N1 virus have been reported to have a safe cardiovascular profile; however, their impact on endothelial function and arterial stiffness has not been established.

Methods: We recruited 25 HIV infected patients (all male, 3 naïve to antiretroviral therapy, mean age 35±10 years) with a good functional status (mean CD4 count: 719±273). All were free from overt cardiovascular disease; 14 patients were vaccinated with a single dose of a monovalent, adjuvanted vaccine against influenza A/H1N1.11 patients were subjected to a sham procedure (controls). Measurements were taken prior to, 8 and 48 hours post vaccination. FMD of the brachial artery was used as an index of endothelial function; carotid-femoral PWV as a measure of arterial stiffness. ADMA, IL-6 and sICAM-1 were measured in blood samples. Comparisons were performed by repeated measures ANOVA.

Results: Vaccination led to a significant impairment of endothelial function, denoting a diminished bioavailability of nitric oxide that persisted even after 48h (baseline: 6.5±4.8 %, 8h: 2.3±4.9%, 48h: 1.8±4.8 %; p=0.05). However, arterial stiffness, as assessed by cfPWV, was not significantly altered (baseline: 7.2±1.2 m/sec, 8h: 7.0±1.2 m/sec, 48h:6.8±0.9 m/sec; p=ns). ADMA, IL-6 and sICAM-1 levels did not change.

Conclusion: Vaccination against influenza A/H1N1 with a monovalent, adjuvanted vaccine leads to endothelial dysfunction in HIV patients, which lasts for at least 48 hours. Given the increased cardiovascular risk of these patients, these findings warrant further research.