Immunization safety requires a modified surveillance system

Vaccines are considered drugs but require different "immunization safety" surveillance systems to monitor adverse events.

Immunization safety is the process of ensuring and monitoring the safety of all aspects of immunization, including:

  • vaccine quality, 
  • adverse events, 
  • vaccine storage and handling, 
  • vaccine administration, 
  • disposal of sharps,
  • management of waste.

The skills and infrastructure to deal with genuine vaccine adverse reactions are essential to public safety, as well as to prevent or manage fear caused by false or unproven signals from patients and health workers. Some of the key differences between vaccines and drugs, which lead to the need for specific AEFI surveillance, are listed in the table below.

Vaccines Other drugs
Who gets them?
Usually, healthy people including infants.

Often most of the population, birth cohort, or group at high risk for disease or complications.
Usually, sick people.
To prevent disease. Usually to treat disease.
How do they get them?
Vaccines are often administered through public health programmes.

In some countries, vaccination may be a prerequisite for enrolment in school.
Often administered by a medical doctor or pharmacist.
When do they get them?
Most childhood vaccines are administered at specific ages, or in relation to special circumstances such as outbreaks or travel.

The age at the time of vaccination may coincide with the emergence of certain age-related diseases (e.g. neurodevelopmental disorders).
Normally at time of illness.
What about adverse events?
Low acceptance of risk.

Intensive investigation of severe AEFIs, even if rare, is necessary.

Minor AEFIs also should be carefully monitored because they may suggest a potentially larger problem with the vaccine or immunization, or have an impact on the acceptability of immunization in general.
Acceptance of adverse events often depends on the severity of illness being treated and the availability of alternative treatment options.
How many?
8–15 Childhood vaccines globally recommended. Thousands of drugs are available.


When parents bring their children for immunization, why may they have a low tolerance for any adverse events that follow?


  • Parents may be anxious about immunization because they are voluntarily exposing their healthy children to the risk of an adverse reaction. Any benefit from the vaccination is not immediate and can only be imagined in terms of protection from future disease.