Guillain-Barré syndrome (GBS) is an autoimmune disorder of the peripheral nervous system that typically develops within 4 weeks after infection. In addition to conventional infectious diseases with which we are familiar, emerging infectious diseases, such as Zika virus infection and coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have also been suggested to be associated with GBS. GBS is mainly categorized into a demyelinating subtype known as acute inflammatory demyelinating polyneuropathy (AIDP) and an axonal subtype known as acute motor axonal neuropathy (AMAN). Most patients who develop GBS after Zika virus infection or COVID-19 have AIDP. The concept of molecular mimicry between pathogens and human peripheral nerve components was established through studies of AMAN with anti-ganglioside GM1 antibodies occurring after Campylobacter jejuni infection. Although such mimicry between specific pathogens and myelin or Schwann cell components has not been clearly demonstrated in AIDP, a similarity of Zika virus and SARS-CoV-2 proteins to human proteins has been suggested. With the development of global commerce and travel, emerging infectious diseases will continue to threaten public health. From this viewpoint, the development of vaccines and antiviral drugs is important to prepare for and control emerging infectious diseases. Although a decrease in the number of patients after the 2015-2016 Zika epidemic increased the difficulty in conducting phase 3 trials for Zika virus vaccines, the efficacy and safety of new vaccines have recently been demonstrated for COVID-19. In general, vaccines can decrease the risk of infectious disease by stimulating the immune system, and discussions regarding an increased risk of autoimmune disorders, such as GBS, have been ongoing for many years. However, the risk of GBS is not considered a legitimate reason to limit the administration of currently available vaccines, as only a trivial association or no association with GBS has been demonstrated.