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Give the answer to the question in picture Refer park For 8 marks Appropriate diagrams necessary
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Adverse Events Following Immunization (AEFI)
Source: Park's Textbook of Preventive and Social Medicine
Definition
An AEFI is any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine. The adverse event may be any unfavourable or unintended sign, abnormal laboratory finding, symptom or disease.
Reported AEFIs can be:
- True adverse events - genuinely a result of the vaccine or immunization process
- Coincidental events - not due to the vaccine but temporally associated with immunization
Cause-Specific Classification (CIOMS/WHO 2012)
| Type of AEFI | Definition |
|---|---|
| Vaccine product-related reaction | Caused by inherent properties of the vaccine product itself |
| Vaccine quality defect-related reaction | Caused by a quality defect in the vaccine product or its administration device |
| Immunization error-related reaction (formerly "programme error") | Caused by inappropriate vaccine handling, prescribing or administration - preventable |
| Immunization anxiety-related reaction (stress-related response) | Arising from anxiety about the immunization |
| Coincidental event | Caused by something other than the vaccine, immunization error, or anxiety |
1. Vaccine Reactions
A. Common Minor Reactions
These arise as part of the immune response to the vaccine. They are expected, self-limiting, and do not indicate harm.
Local reactions (pain, swelling, redness at injection site):
- Occur in ~10% of vaccinees
- Up to 50% with DTP (whole cell) or tetanus boosters
- BCG causes a papule 2+ weeks after, which ulcerates and heals leaving a scar
Systemic reactions (fever, malaise, irritability):
- Fever in ~10% of vaccinees; ~50% with DTP
- Measles/MMR: fever, rash, conjunctivitis in 5-15%
- OPV: diarrhoea, headache, muscle pain in <1%
- Mumps (swollen parotid) and rubella (joint pains) in <1% of children; rubella in 15% of adults
B. Rare, Serious Reactions
| Reaction | Vaccine | Timing |
|---|---|---|
| Anaphylaxis | Any vaccine | Within minutes |
| Febrile seizures | DTP, measles/MMR | 0-2 days (DTP); 6-12 days (measles) |
| Encephalopathy | DTP, measles/MMR | 0-2 days (DTP); 6-12 days (measles) |
| Vaccine-associated paralytic polio (VAPP) | OPV | 4-30 days (recipient); 4-75 days (contact) |
| Thrombocytopenia | Measles/MMR | 15-35 days |
| Intussusception | Rotavirus vaccine | Usually after first dose |
| Disseminated BCG infection | BCG | 1-12 months |
| Lymphadenitis/Osteitis | BCG | 1-12 months |
Anaphylaxis vs Fainting - important distinction:
| Feature | Fainting | Anaphylaxis |
|---|---|---|
| Skin | Pallor, cold clammy | Urticaria, erythema, lip swelling |
| Pulse | Bradycardia | Tachycardia |
| Respiration | Normal/shallow | Tachypnoea, wheezing, stridor |
| Supine position | Relieves symptoms | Does NOT relieve |
| GIT | Vomiting only | Vomiting + diarrhoea + cramps |
Management of anaphylaxis: Adrenaline 1:1000 solution, 0.5 ml IM immediately for adults; repeat every 20 minutes if BP <100 mmHg systolic. Add chlorpheniramine maleate 10-20 mg IM. Observe patient for 30 minutes after any vaccine injection.
2. Immunization Error-Related Reactions
These are preventable reactions caused by errors in handling, prescribing or administering vaccines:
| Error Type | Example | Reaction |
|---|---|---|
| Vaccine handling error | Exposure to excess heat/cold; use after expiry | Agglutination of excipients; loss of potency |
| Prescribing/non-adherence error | Failure to observe contraindication; wrong dose | Anaphylaxis, VAPP, systemic reactions |
| Administration error | Wrong diluent; non-sterile technique | Abscess, sepsis, failure to vaccinate |
Previously, the most common error was infection (HIV, hepatitis B) from non-sterile injection; this has reduced significantly with auto-disabled (AD) syringes. Contaminated vaccine (often Staphylococcus aureus) causes illness within a few hours of administration.
3. Immunization Stress-Related Response
Previously called "immunization anxiety-related reaction." Individuals can react in anticipation of or as a result of any injection. This is a vasovagal (fainting) response and is managed by laying the patient flat.
Reportable AEFIs (Surveillance)
| Time after immunization | Events to report |
|---|---|
| Within 24-48 hours | Anaphylaxis, anaphylactoid reaction, persistent screaming >3 hours, hypotonic-hyporesponsive episode (HHE), toxic shock syndrome |
| Within 7 days | Severe local reaction, sepsis, injection site abscess |
| Within 14 days | Seizures (including febrile), encephalopathy |
| Within 3 months | Acute flaccid paralysis (AFP) |
| Within 1-12 months (BCG) | Lymphadenitis, disseminated BCG, osteitis/osteomyelitis |
| No time limit | Death, hospitalization, disability, or any severe/unusual event thought to be related |
Common minor reactions (local reactions, transient fever) do NOT need reporting.
Investigating AEFI Clusters
A cluster = two or more cases of the same adverse event related in time, place, or vaccine administration.
Flowchart for AEFI Cluster Investigation (Fig. 25, Park's):
The flowchart guides towards:
- Programme error - if all cases from one facility
- Vaccine product-related reaction - if all cases got same vaccine/lot, it is a known reaction, within expected rate, and no similar illness in unvaccinated
- Immunization error or vaccine quality defect - if reaction rate is higher than expected
- Coincidental event - if similar illness exists in unvaccinated people
Prevention of AEFI
- Proper sterilization of syringes and needles
- Proper selection of the subject and the vaccine product
- Observe contraindications carefully
- Measles and BCG vaccines reconstituted only with manufacturer's diluent; discard at end of each session
- No other drugs should be stored beside vaccines in the immunization refrigerator
- Training and close supervision of immunization workers
- Use of Auto-Disabled (AD) syringes to prevent reuse
- Maintain cold chain integrity
- Have adrenaline ready at every immunization session
Summary Diagram - AEFI Classification:
AEFI
├── Vaccine product-related reaction
├── Vaccine quality defect-related reaction
├── Immunization error-related reaction (Preventable)
├── Immunization anxiety/stress-related response
└── Coincidental event
Park's Textbook of Preventive and Social Medicine, Chapter on Immunization - AEFI section (Table 35, Table 36, Table 38, Table 39, Fig. 25)
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