Guillain-Barré Syndrome & Vaccines

Guillain-Barré Syndrome (GBS) is a rare neurological disorder in which the immune system attacks the peripheral nerves. Several vaccines have been associated with rare increases in GBS risk. This page documents the evidence and regulatory assessments.

What is Guillain-Barré Syndrome?

GBS is an autoimmune disorder affecting the peripheral nervous system:

• Mechanism: Immune system mistakenly attacks nerve insulation
• Symptoms: Weakness, tingling, potentially paralysis
• Recovery: Most people recover, though some have lasting effects
• Background rate: Approximately 1-2 cases per 100,000 person-years in general population

Vaccine-Associated GBS: Documented Associations

1976 Swine Flu Vaccine

The most well-established vaccine-GBS association comes from the 1976 influenza vaccine:

• Risk: Approximately 1 additional case per 100,000 vaccinations
• Later vaccines: Subsequent flu vaccines have shown much smaller or no increased risk
• Risk-benefit: Even with this association, flu vaccination benefits outweigh GBS risk for most people

2009 H1N1 Influenza Vaccine

Studies found a small increased risk:

• Estimated risk: Approximately 1-2 cases per million vaccinations
• Compared to infection: Natural H1N1 infection carried significantly higher GBS risk

Janssen (Johnson & Johnson) COVID-19 Vaccine

The FDA and WHO identified a rare GBS signal:

• Estimated risk: Approximately 8-10 cases per million vaccinations (primarily in males 50+)
• Regulatory action: Added warning to vaccine labeling
• Context: Risk remains extremely small; COVID-19 infection carries higher GBS risk

Other Vaccines

Current evidence does not support increased GBS risk for:

• Pfizer-BioNTech or Moderna COVID-19 mRNA vaccines
• MMR vaccine
• Hepatitis B vaccine
• Tetanus, diphtheria, and pertussis vaccines
• Most childhood vaccines

Understanding Absolute Risk

Sources & Citations

• CDC: GBS and Vaccines
• FDA: GBS and Janssen Vaccine