Autoimmune inflammatory polyneuropathy (PN) can be triggered by vaccination. We report 3 such cases. A 36-year-old female nurse presented 15 days after a hepatitis B vaccination (HBV) with acute sensory disturbances in the lower limbs. She had severe ataxia but no weakness. Cerebrospinal fluid (CSF) protein level was 84 mg/100 mL, with 3 lymphocytes. A 66-year-old man presented 21 days after HBV with severe motor and sensory PN involving all 4 limbs. A 66-year-old man presented 15 days after a yellow fever vaccination with progressive motor and sensory PN involving all 4 limbs and bilateral facial paralysis. CSF protein level was 300 mg/100 mL, with 5 lymphocytes. Six weeks later, a tracheostomy was performed. In these 3 patients, the nerve deficits lasted for months. In each case, peripheral nerve biopsy showed KP1-positive histiocytes but no T-lymphocytes in the endoneurium. On ultrastructural examination, there was axonal degeneration in the first 2 cases; in case 2, a few myelinated fibers exhibited an intra-axonal macrophage but the myelin sheath was preserved. There was only 1 example of macrophage-associated demyelination in case 2, but these were numerous in case 3. It is likely that in the first 2 cases, an autoimmune reaction against some axonal or neuronal components was triggered by HBV. It induced an acute sensory ataxic PN in case 1 and an acute motor and sensory axonal neuropathy (AMSAN) in case 2. The third patient had a chronic inflammatory demyelinating PN, likely triggered by yellow fever vaccination.