Exploring the "Two-Hit" Phenomenon of Guillain-Barré Syndrome Following Respiratory Syncytial Virus and Influenza Vaccinations.

Guillain-Barré syndrome (GBS) is a neurological disorder characterized by peripheral, autoimmune-mediated demyelinating polyneuropathy, which can cause muscle weakness and paralysis. While most cases are triggered by respiratory or gastrointestinal infections, vaccinations have also been linked to GBS pathogenesis. The association of the influenza vaccine and GBS, notably prevalent during the 1976 United States swine flu pandemic, has significantly decreased with contemporary seasonal influenza vaccines. At the same time, cases of GBS have been reported with newer vaccines, like the recently approved respiratory syncytial virus (RSV) vaccines. However, their exact relationship with autoimmune demyelinating polyneuropathy remains unknown. In this report, we present a case of a 60-year-old man who developed GBS two weeks after receiving the new Pfizer's RSV vaccine in conjunction with the influenza vaccine for the first time.