RSV vaccines and Guillain-Barré syndrome: Insights into an emerging concern.

Respiratory syncytial virus (RSV) is a common cause of serious lower respiratory tract infections (LTRI), disproportionately affecting infants and older adults. The recent approval of 3 different RSV vaccines marks a significant advancement in mitigating RSV-related morbidity and mortality. However, the increased incidence of Guillain-Barré syndrome (GBS) following RSV vaccination, confirmed by post-marketing surveillance, has raised concerns. Apart from the previously proposed mechanisms that primarily include molecular mimicry and host genetics, electrolytic hydroelectric disorders, particularly the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)-induced hyponatremia, may be associated with GBS. Given that GBS is more common in individuals >65 years - the primary target group for RSV vaccination - this overlap warrants careful consideration. While the benefits of RSV vaccines have been demonstrated, continued safety monitoring and investigation into rare adverse events such as GBS are essential to ensure public health benefits and confidence while minimizing risks.