This medically confirmed literature case (initial receipt 20-Oct-2015) concerns a 62-year-old male patient. On an unspecified date, the patient received influenza vaccine (influenza virus vaccine, manufacturer and batch number not reported). On an unspecified date, following vaccination, the patient experienced an episode of the common cold with leg cramps and lower extremity weakness that progressed to severe paraparesis over 4 weeks. He also developed sensory loss in his lower extremities that ascended to his abdomen with mild numbness in the hands. The patient had severe generalised weakness of proximal and distal muscles (MRC 3/5) with areflexia. He could not stand or walk. His CSF protein was 700 mg/dl without pleocytosis.  EDx (electro diagnostic studies) showed absent sural, superficial fibular, median and ulnar SNAPs with a low amplitude radial SNAP (7microV) and absent fibular and tibial CMAPs. Median and ulnar motor conduction studies showed marked slowing of conduction velocities, borderline CMAP amplitudes, median conduction block in the forearm and markedly prolonged F-waves latencies. These findings were consistent with an acquired demyelinating neuropathy. The patient received treatment with IVIg at 2 g/Kg. Within 4 months, the patient's muscle strength improved slowly and he was able to walk with a walker but had bilateral flail feet. At this point, his neuromuscular score improved from 20/100 at nadir to 65/100. During the next 3-4 months, the patient improved and he showed no further progression. An EDx study showed absent SNAPs diffusely and worsening ulnar and median CMAP amplitudes, conduction blocks in the forearms bilaterally and marked slowing of velocities.  The patient was initiated on treatment with IVIg at 2 g/Kg every 4 weeks.  His condition improved after the treatment. After 5 pulse therapies of IVIg, his neuromuscular score was 90/100. The patient was able to walk with a walker but with residual bilateral foot drop. The patient continued to improve on IVIg. As the patient did not tolerate azathioprine due to pancytopenia, mycofenolate mofetil was added to the IVIg treatment. One year later, the patient walked independently with bilateral ankle-foot orthoses. The treatment with IVIg was increased slowly to every 12 weeks and was discontinued 2 years later. The patient was maintained on mycofenolate. An EDx study at 3 years showed significant improvement in CMAP amplitudes on the upper extremities with partial left median conduction block and persistent slowing of velocities. The SNAPs and lower extremity CMAPS remained absent. The outcome was not reported. The patient had a remarkable clinical and EDx improvement after CIDP (chronic inflammatory demyelinating polyneuropathy) treatment but remained dependent on IVIg during long follow up periods. Reporter's Comments: Reporter's comments: It was reported that the patient with acute-onset chronic inflammatory demyelinating polyneuropathy (A-CIDP) was initially diagnosed with severe GBS but was later confirmed to have CIDP based on the clinical course and electro diagnostic (EDx) studies. Sender's Comments: Company comments: Seriousness: Serious. Medically significant, Disability. Listedness: Unlisted. Brand of vaccine not specified. Assessment according to the CCDS for CSL Inactivated Influenza Virus Vaccine and the Afluria PI, CIDP and all associated events are unlisted. Nasopharyngitis (common cold) is also unlisted. Causality: Possible. Time to onset not specified but a close temporal association of within 4 weeks of vaccination was implied. Although the mechanistic evidence of an association between influenza vaccine and CIDP is weak, it can be explained as a autoimmune phenomenon which can follow Influenza vaccination. Of note, patient had an episode of common cold (viral illness) which may have been an alternate risk factor. However there is a temporal association with Influenza vaccination, hence causally attributable.