Like anything else, it really depends on the odds of each side effect. If it's one in a million I don't worry.
Here's the adverse events table from one of clinical trials, look at table 3 if this link isn't direct:
Vast majority are from immunosuppression, colds, upper respiratory infection, etc, etc. The most common TEAEs were UC [6.5%], hypertension [5.9%], upper respiratory infection [5.9%] and increased gamma glutamyltransferase [5.3%] [Table 3]. Two patients experienced macular oedema or thickening due to retinal vein thrombosis that did not require study discontinuation
Treatment-emergent adverse events [TEAEs] leading to study drug discontinuation during the OLE were reported for 17 patients [10%; eight originally in the ozanimod HCl 0.5 mg group, four in the ozanimod HCl 1 mg group and five in the placebo group during the double-blind treatment period]. These events included UC [n = 4; discontinuation due to pleurisy also reported in one of the four patients], adenocarcinoma of unknown origin [n = 1], cholestasis [n = 1], colitis [n = 1], dysplasia [n = 1], erysipelas [n = 1], haemolytic anaemia and jaundice [n = 1], hypochromic anaemia [n = 1], hyperbilirubinaemia and autoimmune haemolytic anaemia [n = 1], interstitial lung disease [n = 1], ischaemic stroke [n = 2], spontaneous abortion [n = 1] and thrombocytopenia [n = 1].
The most commonly reported serious adverse events [SAEs] were UC [n = 6], anaemia [n = 2] and ischaemic stroke [n = 2] [Table 3]; none of these were considered related to study treatment as assessed by the study investigator.
Yes i agree this not sound too good.