Association Between Guillain-Barré Syndrome and COVID-19 Infection and Vaccination: A Population-Based Nested Case-Control Study.

BACKGROUND AND OBJECTIVES: Existing data regarding occurrence of Guillain-Barré syndrome (GBS) after coronavirus disease 2019 (COVID-19) infection and vaccination are inconclusive. We aimed to assess the association between GBS and both severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19 vaccine. METHODS: We conducted a nested case-control study in a cohort of 3,193,951 patients aged 16 years or older, without a diagnosis of prior GBS, from the largest health care provider in Israel. Participants were followed from January 1, 2021, until June 30, 2022, for the occurrence of GBS. Ten randomly selected controls were matched to each case of GBS on age and sex. We assessed both SARS-CoV-2 infection and COVID-19 vaccine administration in the prior 6 weeks in cases and controls. RESULTS: Overall, 76 patients were diagnosed with GBS during follow-up and were matched to 760 controls. A positive test for SARS-CoV-2 was detected in 9 (11.8%) cases and 18 (2.4%) controls. An administration of COVID-19 vaccine was detected in 8 (10.5%) cases (all Pfizer-BioNTech [BNT162b2] vaccine) and 136 (17.9%) controls (134 Pfizer-BioNTech vaccine). Multivariable conditional logistic regression models showed that the odds ratio for GBS associated with SARS-CoV-2 infection and COVID-19 vaccine administration was 6.30 (95% CI 2.55-15.56) and 0.41 (95% CI 0.17-0.96), respectively. The results were similar when exposure to SARS-CoV-2 infection or COVID-19 vaccine administration was ascertained in the prior 4 and 8 weeks, although did not reach statistical significance for COVID-19 vaccine at 4 weeks. DISCUSSION: Our study suggests that SARS-CoV-2 infection is associated with increased risk of GBS, whereas Pfizer-BioNTech COVID-19 vaccine is associated with decreased risk of GBS.

Association between COVID-19 vaccination and myasthenia gravis: A population-based, nested case-control study.

BACKGROUND: Existing data regarding the link between COVID-19 vaccine and myasthenia gravis (MG) are scarce. We aimed to assess the association between Pfizer-BioNTech vaccine with both new-onset MG and MG exacerbation. METHODS: For the first aim, we conducted a nested case-control study in a cohort of 3,052,467 adults, without a diagnosis of MG, from the largest healthcare provider in Israel. Subjects were followed from January 1, 2021 until June 30, 2022 for the occurrence of MG. Ten randomly selected controls were matched to each case of new-onset MG on age and sex. For the second aim, a nested case-control study was conducted in a cohort of 1446 MG patients. Four randomly selected MG patients (controls) were matched to each case of MG exacerbation. Exposure to COVID-19 vaccine in the prior 4 weeks was assessed in cases and controls. RESULTS: Overall, 332 patients had new-onset MG and were matched with 3320 controls. Multivariable conditional logistic regression models showed that the odds ratio (OR) for new-onset MG, associated with COVID-19 vaccine, was 1.14 (95% CI 0.73-1.78). The results were consistent in sensitivity analysis that used more stringent criteria to define MG. Overall, 62 patients with MG exacerbation were matched to 248 MG controls. The multivariable OR for MG exacerbation, associated with COVID-19 vaccine, was 1.35 (95% CI 0.37-4.89). All results were similar when the prior exposure to COVID-19 vaccine was extended to 8 weeks. CONCLUSION: This study suggests that Pfizer-BioNTech vaccine is not associated with increased risk of new-onset nor exacerbation of MG.