A key part of ensuring vaccine safety is continuously monitoring and reporting health events that occur either during or after the immunization process. This is also known as surveillance. According to the Pan American Health Organization, Events Supposedly Attributable to Vaccination or Immunization (ESAVI) refers to any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine. This includes any unfavourable or unintended sign, abnormal laboratory finding, symptom, or disease.
An ESAVI can be serious or non-serious. A non-serious ESAVI is a condition that doesn't pose a significant risk to the vaccinated person, requires no treatment, doesn't require hospitalization, and doesn't cause long-term disability. On the other hand, a serious ESAVI occurs when it causes serious physical harm, requires hospitalization, causes persistent disability, is suspected of causing congenital abnormality, stillbirth, or abortion, or in some cases death. These, however, are rare instances.
Source: Manual for Surveillance of Events Supposedly Attributable to Vaccination or Immunization in the Region of the Americas. Washington, D.C.: Pan American Health Organization; 2022. License: CC BY-NC-SA 3.0 IGO. https://doi.org/10.37774/9789275123867.
