AEFI Basics - Defining the Drama
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Definition: An Adverse Event Following Immunization (AEFI) is any untoward medical occurrence post-immunization, not necessarily causally linked. It includes any unfavorable sign, lab finding, symptom, or disease.
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WHO Classification of AEFIs: 📌 Mnemonic: People Quality Errors Anxiety Coincidence (PQEAC)
Category Description Vaccine Product-related Caused by inherent vaccine properties. Vaccine Quality defect-related Due to vaccine quality defects. Immunization Error-related From inappropriate handling, prescribing, or administration. Immunization Anxiety-related Arising from anxiety (e.g., vasovagal syncope, often immediate). Coincidental event Unrelated; chance occurrence around vaccination time.
⭐ Immunization anxiety-related reactions (IARR) can mimic allergic reactions but are distinguished by context and symptoms like hyperventilation or fainting before/during injection.
Common Culprits - Everyday Vaccine Vibes
Minor AEFIs are frequent but generally self-limiting, categorized as:
- Local reactions: Pain, swelling, redness, or nodule at the injection site.
- Systemic reactions: Fever (often <38.5°C), malaise, myalgia, headache.
| Vaccine | Common Local AEFI | Common Systemic AEFI |
|---|---|---|
| BCG | Pain, papule → ulcer → scar (normal evolution) | Mild fever (uncommon) |
| DPT (wP) | Pain, swelling, redness, nodule; sterile abscess | Fever >38.5°C, irritability, prolonged crying |
| Measles/MMR | Mild pain, redness at site | Fever (7-12 days post), transient morbilliform rash |
| OPV (Oral) | N/A | Rarely: mild fever, vomiting, diarrhea |
Serious Signals - When Vaccines Worry
| AEFI | Key Features | Vaccine(s) | Onset Window |
|---|---|---|---|
| Anaphylaxis | Rapid multi-system allergy. 📌 Epi IM ASAP! (0.01 mg/kg (max 0.5 mg) 1:1000 IM) | Any | <30 min |
| Encephalopathy/Encephalitis | Altered LOC, seizures, focal deficits | Measles, Pertussis (DTP) | Days-weeks |
| Seizures (febrile/afebrile) | Convulsions (febrile common) | MMR, DTP, Influenza | 1-14 days |
| GBS (Guillain-Barré) | Ascending paralysis, areflexia | Influenza, MenACWY | Days-6 wks |
| Thrombocytopenia | ↓Platelets, petechiae | MMR, Varicella | 1-6 wks |
| HHE | Pallor, hypotonia, ↓response; self-resolves | Pertussis-containing | <48 hrs |
| VAPP | Acute flaccid paralysis | OPV | 4-30 days |
| Disseminated BCG | Systemic BCG (immunocompromised) | BCG | Wks-months |
| TTS | Thrombosis + ↓Platelets | Adenoviral vector COVID-19 | 4-28 days |
| Myocarditis/Pericarditis | Chest pain, dyspnea, ECG Δs | mRNA COVID-19, Smallpox | Days-weeks |
AEFI Action Plan - Investigate & Intervene
- AEFI Reporting (India):
- Serious AEFI (death, disability, hospitalization, cluster): Report to DIO/Health Facility within 24 hours.
- DIO: Leads investigation, ensures report completion, facilitates causality assessment.
- Causality Assessment (WHO):
- Determines vaccine-event link.
- Categories:
- Consistent causal association
- Indeterminate
- Inconsistent (coincidental)
- Unclassifiable
- Management:
- Minor: Symptomatic (e.g., paracetamol for fever, cold compress for local pain).
- Severe: Prompt referral to higher facility, emergency care (e.g., adrenaline for anaphylaxis).
⭐ Causality assessment of AEFIs is crucial to differentiate true vaccine reactions from coincidental events, ensuring public trust in immunization programs.
High-Yield Points - ⚡ Biggest Takeaways
- AEFI: Any untoward medical event post-immunization, causality not implied.
- Types: Vaccine reaction, programmatic error, injection reaction (anxiety), coincidental event.
- Most common: Mild fever, local pain/swelling/redness.
- Serious AEFIs: Anaphylaxis (treat with adrenaline), GBS, encephalopathy, febrile seizures.
- BCG: Suppurative lymphadenitis (ipsilateral axillary) is a known AEFI.
- Programmatic errors: Unsterile injection, wrong vaccine/dose/route, reconstitution error.
- AEFI surveillance is vital for vaccine safety and maintaining public trust.
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