C5 and meningococcal infection: Therefore, we based the high dose eculizumab and repeated drug administration on the results of a previous study, in which we found that the CSF C5a concentration in aSAH patients is increased >1400 times on day 1 after ictus compared to the CSF C5a concentration in control patients and slowly decreased until day 10 after ictus.6 Because SAH is an acute disease, it was not possible to vaccinate patients against meningococcal disease 2 weeks in advance, as is recommended in patients with a chronic disease treated with eculizumab.8