Table 2

Criteria for causality assessment for Guillain-Barré syndrome (GBS) in temporal association with vaccination

Proposed causality labelGeneric assessment criteria based on WHO Causality Assessment20Proposed GBS specific causality assessment criteria
ConfirmedPublished peer-reviewed epidemiological evidence supporting causative association with the vaccination
AND
Typical time frame
AND
No indication of another cause for the event
AND
No illness, pre-existing condition or risk factors that could have contributed to the event, as excluded by detailed history, clinical examination and investigations		Administration of a vaccine confirmed to increase risk of GBS
AND
Event ≥24 hours and ≤6 weeks from vaccination19
AND
No indication of an alternative aetiology, including symptoms of infectious illness in the preceding 6 weeks* as excluded by detailed history, clinical examination and investigations
ProbableTypical time frame
AND
No indication of another cause for the event
AND
No illness, pre-existing condition or risk factor that could have contributed to the event, as excluded by detailed history, clinical examination and investigations		Event ≥24 hours and ≤6 weeks from vaccination19
AND
No indication of an alternative aetiology, including symptoms of infectious illness in the preceding 6 weeks* as excluded by detailed history, clinical examination and investigations
PossiblePlausible time frame but outside of typical
OR
There may be an indication of another cause, predisposing condition and/or risk factors, but these are unlikely to fully explain the event		Event >6 weeks and <12 weeks from vaccination19
OR
Clinical or microbiological evidence of an infection, but not one of those which has a proven link to GBS (listed further), or a physiological stress, in the 6 weeks preceding the event
UnlikelyTimeframe not fitting with the event
OR
Evidence of another cause, predisposing condition and/or risk factors that fully explain the event		Event <24 hours or >12 weeks from vaccination19
OR
Clinical suspicion or microbiological evidence of infection with: Campylobacter jejuni, influenza, Cytomegalovirus, Epstein–Barr virus, Mycoplasma pneumoniae, Haemophilus influenzae, hepatitis E, or Zika virus in a typical timeframe; or treatment with tumour necrosis factor antagonist, immune-checkpoint inhibitor or type I interferon4 22 53

  • *This excludes symptoms of reactogenicity such as fever, myalgia and fatigue in the first 72 hours after vaccination.54 While most antecedent infections precede GBS by 4 weeks, a longer cut-off was selected based on the previous reports of GBS occurring up to 6 weeks post-influenza infection.55