Guillain-Barré syndrome following influenza vaccination: A 15-year nationwide population-based case-control study

Assessment of potential adverse events following the 2022-2023 seasonal influenza vaccines among U.S. adults aged 65 years and older

BACKGROUND

While safety of influenza vaccines is well-established, some studies have suggested potential associations between influenza vaccines and certain adverse events (AEs). This study examined the safety of the 2022-2023 influenza vaccines among U.S. adults ≥ 65 years.

METHODS

A self-controlled case series compared incidence rates of anaphylaxis, encephalitis/encephalomyelitis, Guillain-Barré Syndrome (GBS), and transverse myelitis following 2022-2023 seasonal influenza vaccinations (i.e., any, high-dose or adjuvanted) in risk and control intervals among Medicare beneficiaries ≥ 65 years. We used conditional Poisson regression to estimate incidence rate ratios (IRRs) and 95 % confidence intervals (CIs) adjusted for event-dependent observation time and seasonality. Analyses also accounted for uncertainty from outcome misclassification where feasible. For AEs with any statistically significant associations, we stratified results by concomitant vaccination status.

RESULTS

Among 12.7 million vaccine recipients, we observed 76 anaphylaxis, 276 encephalitis/encephalomyelitis, 134 GBS and 75 transverse myelitis cases. Only rates of anaphylaxis were elevated in risk compared to control intervals. With all adjustments, an elevated, but non-statistically significant, anaphylaxis rate was observed following any (IRR: 2.40, 95% CI: 0.96-6.03), high-dose (IRR: 2.31, 95% CI: 0.67-7.91), and adjuvanted (IRR: 3.28, 95% CI: 0.71-15.08) influenza vaccination; anaphylaxis IRRs were 2.54 (95% CI: 0.49-13.05) and 1.64 (95% CI: 0.38-7.05) for persons with and without concomitant vaccination, respectively.

CONCLUSIONS

Rates of encephalitis/encephalomyelitis, GBS, or transverse myelitis were not elevated following 2022-2023 seasonal influenza vaccinations among U.S. adults ≥ 65 years. There was an increased rate of anaphylaxis following influenza vaccination that may have been influenced by concomitant vaccination.

The role of vaccines in the COVID-19 pandemic: what have we learned?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged late in 2019 and caused the coronavirus disease 2019 (COVID-19) pandemic that has so far claimed approximately 20 million lives. Vaccines were developed quickly, became available in the end of 2020, and had a tremendous impact on protection from SARS-CoV-2 mortality but with emerging variants the impact on morbidity was diminished. Here I review what we learned from COVID-19 from a vaccinologist's perspective.

Hospital-diagnosed morbidities and recent surgery as risk factors for developing Guillain-Barré syndrome

BACKGROUND AND PURPOSE

This study was undertaken to determine the association of hospital-diagnosed morbidity and recent surgery with risk of subsequent Guillain-Barré syndrome (GBS) development.

METHODS

We conducted a nationwide population-based case-control study of all patients with first-time hospital-diagnosed GBS in Denmark between 2004 and 2016 and 10 age-, sex-, and index date-matched population controls per case. Hospital-diagnosed morbidities included in the Charlson Comorbidity Index were assessed as GBS risk factors up to 10 years prior to the GBS index date. Incident major surgery was assessed within 5 months prior.

RESULTS

In the 13-year study period, there were 1086 incident GBS cases, whom we compared with 10,747 matched controls. Any pre-existing hospital-diagnosed morbidity was observed in 27.5% of GBS cases and 20.0% of matched controls, yielding an overall matched odds ratio (OR) of 1.6 (95% confidence interval [CI] = 1.4-1.9). The strongest associations were found for leukemia, lymphoma, diabetes, liver disease, myocardial infarction, congestive heart failure, and cerebrovascular disease, with 1.6- to 4.6-fold increased risks of subsequent GBS. GBS risk was strongest for morbidities newly diagnosed during the past 5 months (OR = 4.1, 95% CI = 3.0-5.6). Surgical procedures within 5 months prior were observed in 10.6% of cases and 5.1% of controls, resulting in a GBS OR of 2.2 (95% CI = 1.8-2.7). Risk of developing GBS was highest during the first month following surgery (OR = 3.7, 95% CI = 2.6-5.2).

CONCLUSIONS

In this large nationwide study, individuals with hospital-diagnosed morbidity and recent surgery had a considerably increased risk of GBS.

Triggers of Guillain-Barré Syndrome: Campylobacter jejuni Predominates

Guillain-Barré syndrome (GBS) is a rare immune-mediated acute polyradiculo-neuropathy that typically develops after a previous gastrointestinal or respiratory infection. This narrative overview aims to summarise and discuss current knowledge and previous evidence regarding triggers and pathophysiology of GBS. A systematic search of the literature was carried out using suitable search terms. The most common subtypes of GBS are acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN). The most common triggers of GBS, in three quarters of cases, are previous infections. The most common infectious agents that cause GBS include Campylobacter jejuni (C. jejuni), Mycoplasma pneumoniae, and cytomegalovirus. C. jejuni is responsible for about a third of GBS cases. GBS due to C. jejuni is usually more severe than that due to other causes. Clinical presentation of GBS is highly dependent on the structure of pathogenic lipo-oligosaccharides (LOS) that trigger the innate immune system via Toll-like-receptor (TLR)-4 signalling. AIDP is due to demyelination, whereas in AMAN, structures of the axolemma are affected in the nodal or inter-nodal space. In conclusion, GBS is a neuro-immunological disorder caused by autoantibodies against components of the myelin sheath or axolemma. Molecular mimicry between surface structures of pathogens and components of myelin or the axon is one scenario that may explain the pathophysiology of GBS.