Immunization error-related reaction

Classification of AEFIs

Immunization errors result from errors in vaccine preparation, handling, storage or administration. They are preventable and detract from the overall benefit of the immunization programme. The identification and correction of these incorrect immunization practices are of great importance.

Immunization errors can result in a cluster of events, defined as two or more cases of the same adverse event related in time, place or vaccine administered. These clustersClusterTwo or more instances of an event related in time, place, population subgroup, or common exposure (e.g., vaccine). AEFI clusters are usually associated with a particular provider, health facility, and/or a vial of vaccine that has been inappropriately prepared or contaminated. are usually associated with a particular provider or health facility, or a vial of vaccine that has been inappropriately prepared or contaminated. Immunization errors can also affect many vials, for example, freezing vaccine during transport may result in an increase in local reactions.

Examples of immunization errors and possible AEFIs

Immunization error Possible AEFI
Non-sterile injection
  • Reuse of disposable syringe or needle leading to contamination of the vial, especially in multi-dose vials,
  • Improperly sterilized syringe or needle,
  • Contaminated vaccine or diluent.
Reconstitution error
Injection at incorrect site
Vaccine transported/stored incorrectly
  • Freezing vaccine during transport,
  • Failure to keep vaccine in cold chain, exposing to excessive heat or cold.
  • Increased local reaction from frozen vaccine,
  • Ineffective vaccine*
ContraindicationContraindicationA condition that makes a particular treatment or procedure, such as vaccination with a particular vaccine, inadvisable. Contraindications can be permanent, such as known allergies to a vaccine component, or temporary, such as an acute febrile illness. ignored
  • Vaccination staff ignoring or not becoming familiar with contraindications for a vaccine.
Avoidable severe reaction

* Ineffective vaccine is not strictly an adverse event; it is a vaccine failure.


What immunization error can most likely occur if vaccines are kept in the same refrigerator as other drugs?

A. The vaccine could be stored incorrectly.
B. Contraindication could be ignored.
C. A reconstitution error might occur.
D. The injection may be non-sterile.
E. The injection may occur at the wrong site.


Answer C is correct.

  • Incorrect storage can lead to reconstitution errors: The drug may be given to the client in mistake for a vaccine or may be used instead of the correct diluent to reconstitute a freeze-dried powder vaccine.

WHO's Immunization in Practice, Module 658 entitled "Holding an immunization session" includes the correct technique for giving each vaccine.

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It is vital that health workers or local vaccinators are trained to store and handle vaccines properly, reconstitute and administer vaccinations correctly, and have the right equipment and materials to do their job.