Recap of diagnosis and treatment
For decades, the diagnosis of GBS has relied on the presence of symptoms, including progressive weakness and loss of reflexes and sensations. Nerve-conduction studies and cerebrospinal fluid evaluation can help confirm the diagnosis.
IVIg shortens recovery, said Dr. Lunn, although nothing cures GBS. “And that’s a common problem: Clinicians think that they’re going to give somebody IVIg, and the patient’s going to get better immediately.” When that doesn’t happen, he said, physicians are tempted to give a second immunoglobulin dose.
However, a study published in 2021 shows that a second IVIg dose does not result in faster or better improvement – only in a significant risk of cardiovascular, cerebrovascular, and other thrombotic events 3 weeks later.8 Dr. Lunn noted that, although adverse-event data were “buried” in the supplemental materials of that study, the high cost of IVIg (approximately $12,500 per dose) means that the study has changed practice for the benefit of patients, providers, and health care systems.
COVID-19 and GBS triggers
Campylobacter jejuni infection still accounts for 30% to 40% of GBS cases, followed by other bacteria, including Mycoplasma pneumoniae and Haemophilus influenzae, and then by viruses, including cytomegalovirus and, rarely, human immunodeficiency virus. In recent years, severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection – COVID-19 – and vaccines against the viral infection have captured headlines for purportedly being a cause of GBS.
The Zika virus epidemic of 2015-2016 has been linked to GBS-like illness. The 2003 severe acute respiratory syndrome (SARS) pandemic and the Middle East respiratory syndrome coronavirus (MERS-CoV) epidemic were associated with GBS – although, taken together, SARS and MERS-CoV produced fewer than 10 cases of GBS, Dr. Lunn noted. Nevertheless, heightened awareness of these viruses fueled hypervigilance regarding the prospect that COVID-19 could cause GBS. Following reports of a single such case in Wuhan and hundreds in Italy, worry over pandemic GBS grew worldwide.
Dr. Lunn and colleagues addressed the COVID-19–GBS question in a 2023 publication.9 “Because GBS is largely treated only with IVIg, and IVIg costs a lot of money, and the U.K. government insists on every dose of IVIg being logged in a government database, we were able to identify virtually every case of GBS,” he said.
GBS diagnoses were reliable, he added, because each case was confirmed by physicians outside the emergency department. Analysis revealed that, in 2020, U.K. GBS cases actually declined by around one-third. “And even when there was a second wave of COVID-19 at the end of 2020, partly caused by better counting,” Dr. Lunn said, “there was no further increase in GBS cases. We concluded that there was no link between GBS and COVID-19, as the cases simply didn’t appear.”
The foregoing findings have since been corroborated by studies in Singapore, the United States, and South America, he pointed out. Earlier case series suggesting a link between COVID-19 and GBS were selective, Dr. Lunn added, with numbers too small to support robust conclusions.
The lack of a causal link between COVID-19 and GBS suggested to Dr. Lunn that there was no reason COVID-19 vaccination should cause GBS. All COVID-19 vaccines were designed to provoke an immune response either (1) by producing the SARS-CoV-2 spike protein on the surface of virus (through a replication-incompetent adenoviral vector) or (2) through DNA or mRNA transcription, he explained. “The spike protein is only a small part of COVID-19.”