WHO/V&B/AVI

Adverse Events Following Immunization, AEFI

A brief presentation on the adverse events following immunization, monitoring for AEFIs and taking

actions when events occur

WHO/V&B/AVI

Adverse Events Following Immunization, AEFI

Adverse events following immunization are events or reactions observed following immunization. Some of these events may be due to the vaccine, some due to error in the administration of the vaccine

There is no vaccine that is 100% safe & without any risks

Such events may range from mild side effects to life-threatening, but rare, illnesses

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AEFI

Mild Reactions Mild reactions following immunization

are common They include pain & swelling at the site

of injection, fever, irritability, malaise They are self-limiting, hardly requiring

even symptomatic treatment But it is important to reassure parents

about such events so that they know about it

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AEFI

Rare, more severe reactions Severe reactions are rare Such reactions include seizures,

thrombocyto-paenia, hypotonic hyporesponsive episodes, persistent inconsolable screaming

In most cases they are self-limiting and lead to no long-term problems

Anaphylaxis, while potentially fatal, is treatable without any long-term effects

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Examples of types & frequency of AEFIs (in some common vaccines)

Vaccine ReactionOnset

IntervalRates per

million dosesSuppurative lymphadenitis 2-6 months 100 to 1000BCG osteitis 1-12 months 1 to 700Disseminated BCG-it is 1-12 months 2

Hib Nil knownAnaphylaxis 0-1 hour 0 to 2

Guillain-Barrè Syndrome (plasma derived) 1-6 weeks 5Febrile seizures 5-12 days 333Thrombocytopaenia 15-35 days 33Anaphylaxis 0-1 hour 1 to 50

OPV Vaccine associated paralytic polio (VAPP) 4-30 days 1.4 to 3.4Persistent (>3 hrs) inconsolable crying 0 -24 hours 1000 to 60000Seizures 0 - 3 days 570Hypotonic, hyporesponsive episode 0-24 hours 570Anaphylaxis 0 - 1 hour 20Encephalopathy 0 - 3 days 0 to 1

Post-vaccination encephalitis 7-21 days400 to 4000 (in infants <6 m)

Allergic/anaphylaxis 0-1 hour 5 to 20Yellow Fever

BCG

Hepatitis B

Measles/MMR

DTP

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AEFIAvoiding Programme Errors

Use sterile needle & syringe for every injection Reconstitute only with specific diluent Discard reconstituted vaccines after six hours Do not store drugs & other medicines in the

same fridge as the vaccines and diluents Train & supervise health workers to ensure

safe injection practices Monitor, Investigate and Act when AEFIs occur

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AEFI

Why monitor AEFI? No vaccines are 100% safe and without

any risks It is important to know the risks and how

to handle such an event when it occurs Informing people correctly on AEFI helps

keep public’s confidence in the immunization programmes

Monitoring AEFI also helps improve the quality of service

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AEFI

Steps in AEFI surveillance Detection and reporting Investigation Data analysis Corrective and other actions Evaluation

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AEFIDetection and reporting

Every individual that administers an immunization injection should know about AEFI

There should be a national system for detecting and reporting of AEFI

At least the following should be included in the national AEFI monitoring system- “trigger events”All injection site abscessesAll cases of BCG lymphadenitisAll deaths suspected to be related to

immunizationAll hospitalisation suspected to be related to

immunization

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AEFI

Detection and reporting The above basic categories act as “trigger”

mechanisms for further course of action The national monitoring system should define

the flow of information and mechanisms for taking actions

While minor events may be recorded and reported as a routine activity to be analysed only at periodic times, sudden, unexplained deaths or large scale hospitalisation or a cluster of events reported following immunisation warrants immediate investigation

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AEFIInvestigation

AEFI investigation will attempt to confirm or propose alternative diagnosis of the

reported eventidentify the specifications of the vaccine incriminatedexamine the operational aspects of the programmeidentify whether it was an isolated event or a cluster

of events and, if a cluster, where the immunization was given and what vaccines were used

Preliminary investigation may be carried out by the local health worker, but serious AEFIs or clusters of AEFIs should be investigated by special teams from district or central level

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AEFI

Investigation Data on the patient(s); vaccine (lot number,

expiry, manufacturer, lab results if any), storage, reconstitution practice, diluent used, general disease information in the area, similar disease episodes in unimnunized persons in the same locality, etc. should be collected

Collect samples of vaccines and diluents used (make sure vaccine sample collected are kept in the cold chain)

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AEFI: An example of an AEFI investigation

Background It is reported that following a measles campaign

in a primary school in District X, several children had convulsions. It was widely rumoured that the measles injection was responsible for it

Hypothesis that the reported health event (convulsion) was

an AEFI following measles vaccination

Define the case You define your ‘case’ as any child in that primary school

who received measles injection on that particular day and

had convulsions.

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AEFI: example contd..Case investigation

Line list all children, with age & sex, who had received measles injection on that day

Find those that reported to have had convulsions Find out all the details regarding the convulsions-

onset time after immunization, manner of convulsion, recovery following the convulsion, concomitant medications, fever, any other health problems. Determine the quality of the vaccine (expiry, storage), reconstitution, diluent, injection process, etc.

Take samples of the vaccine vials used for lab testing

Scrutinise the stock entries, stock balance, etc.

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AEFI: example contd..

One child had an attack of fit half an hour after the immunization. Following this three other children had fainting spells in the same class. All recovered spontaneously although the child who had the first convulsion took longer to recover. Also, the first child sustained a minor cut on the forehead from the fall

Next day, five more children called in sick on grounds that they had also attacks of fits after the school

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AEFIData analysis

Once the data is collected, it should be analysed as quickly as possible to determine whether the AEFI is

Programme related (incorrect dose of vaccine, wrong site, wrong diluent, improper storage & handling, use of other medicines as diluent, etc.)

Vaccine induced AEFI Coincidental AEFIs (caused by something other than

vaccine or programme errors)Unknown

Laboratory supportIf patient hospitalised, tests may confirm diagnosisTesting vaccines often yield doubtful answersSend case investigation report with vaccine for test

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AEFI: example contd..

Data Analysis You find that the vaccine used has not expired, was well

maintained in the cold chain, correct diluent was used, There was no evidence of contamination, the health

workers always discarded reconstituted vaccine at the end of the session.

The medical history showed that the fits which the other children had were mere fainting spells, lasting only for a few moment, with spontaneous recovery. No subsequent attacks occurred

The index child had a true convulsion. No fever or other illnesses at that time.

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AEFI: example contd..

However, going over the medical history of the child, the health worker recalled that last year the same child had an episode of convulsion for which he had provided treatment. He had advised that the parents should consult a medical or a neurological expert for further management. On questioning, it was found that the parents did not have the time or the money to do that and it was felt that it would resolve naturally

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AEFICorrective and other actions

Action must not wait for investigation to be completed

Treat the patient(s) as the first response Communicate, inform the public, parents,

media people on the event, actions being taken & next steps

Once the investigation is completed, publicise the results

Take corrective actions, where necessary Training of health workers & supervision to

prevent avoidable AEFIs in future

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AEFI: example contd..

Conclusion From the available information, and

based on the data analysis, you conclude that event was not an AEFI, but Coincidental.

Following this, you will take time to explain to the parents, teachers and the community about the event, your investigation and your final conclusions.

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AEFIEvaluation

Like any other surveillance systems, AEFI surveillance must also be evaluated periodically to examine its usefulness and to modify it if necessary

Issues to consider when evaluating a surveillance system aretimeliness, completeness, accuracy of the systemswiftness with which response was effected when

a trigger event was reportedappropriateness of actions takenpotential for strengthening of immunization

system

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AEFI

An ounce of prevention is always better than a pound of cure. Good

training & close supervision of health workers, coupled with a functioning surveillance system for monitoring &

reporting are the best guarantee against the likelihood of an event

occurring at all