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8 Adverse Events Following Immunization

Description | Specific Indicators | Corresponding OPHS outcomes | Corresponding National Indicators | Data Sources |  Alternative Data Sources | ICD Codes | Analysis Check List | Method of Calculation |  Basic Categories | Indicator Comments | Cross-References to Other Sections | References | Acknowledgements | Changes Made
Number of adverse events following immunization (AEFI) in a specified time period. 
Specific Indicators
  • Number of adverse events following immunization in a specified time period

Corresponding Outcome from the Ontario Public Health Standards (OPHS) 

The Ontario Public Health Standards (OPHS) establish requirements for the fundamental public health programs and services carried out by boards of health, which include assessment and surveillance, health promotion and policy development, disease and injury prevention, and health protection. The OPHS consist of one Foundational Standard and 13 Program Standards that articulate broad societal goals that result from the activities undertaken by boards of health and many others, including community partners, non-governmental organizations, and governmental bodies. These results have been expressed in terms of two levels of outcomes: societal outcomes and board of health outcomes. Societal outcomes entail changes in health status, organizations, systems, norms, policies, environments, and practices and result from the work of many sectors of society, including boards of health, for the improvement of the overall health of the population. Board of health outcomes are the results of endeavours by boards of health and often focus on changes in awareness, knowledge, attitudes, skills, practices, environments, and policies. Boards of health are accountable for these outcomes. The standards also outline the requirements that boards of health must implement to achieve the stated results.

Link to OPHS

Outcomes Related to this Indicator

  • Societal Outcomes (Vaccine Preventable Diseases); There is a reduced incidence rate of adverse events following immunization
  • Board of Health Outcomes (Vaccine Preventable Diseases): Health care providers report adverse events following immunization to the board of health; The board of health achieves timely and effective detection and identification of adverse events following immunization.

Corresponding Health Indicator(s) from Statistics Canada and CIHI

  • None

Data Sources
Numerator: Reportable Disease Data
Original source: Integrated Public Health Information System, [Public Health Unit]
Distributed by: Public Health Unit
Suggested citation (see Data Citation Notes):
iPHIS [years], Extracted: [date]
Analysis Check List

  • Consider aggregation of data values and/or cell suppression when appropriate when dealing with small numbers to avoid risk of confidentiality breach. A new resource is currently under development to provide more detailed information on this issue.
  • The iPHIS field called "Adverse Event(s) Reaction(s)/Onset Date/Time" is available in Cognos ReportNet 2.0 reporting software. This field represents the most epidemiologically accurate date to which to assign the event, however it may not be consistently entered despite the fact that it is a required field in the draft MOHLTC AEFI User Guide (found on the public health Ontario portal in the "iPHIS Ontario" workspace under "Draft User Guides" folder and "VPD" subfolder.  A username and password are required for this portal)
  • The iPHIS field called "Episode Accurate Date" represents a hierarchy of dates in iPHIS: symptom onset date, specimen collection date, lab test date and reported date. This field will always produce a value thus it may be the most complete field to which to assign AEFI's. Symptom onset date in this hierarchy returns the earliest date entered in the standard symptom screen found in the other Outbreak Module diseases.  This symptom screen is inconsistently completed across health units however reported date is a system-mandatory field in iPHIS thus there it will always contain a value.
  • The iPHIS field called "Administration Date" will return the date that the associated immunization is administered to the client.  This date field may be used to measure AEFIs associated with a particular immunization period
  • To be consistent with MOHLTC reports, include only confirmed cases

Method of Calculation  

Total number of adverse events following immunization in a specified time period.

Basic Categories

  • Age groups for age-specific rates: <1, 1-9, 10-19, 20-44, 45-64, 65-74, 75+, total
  • Geographic areas: public health unit
  • By vaccine type and lot number

Indicator Comments

  • Provincial adverse events following immunization are defined in Appendix B: Provincial Case Definitions for Reportable Diseases of the Ontario Public Health Standards Infectious Diseases Protocol, 2009
  • National adverse events following immunization definitions are still draft.
  • Vaccine types and schedules are subject to frequent change.
  • Data on adverse events following immunization are reported to the health unit by physicians, the public or health unit staff.
  • Persons with adverse events following immunization are entered into the integrated Public Health Information System (iPHIS) and the event is reported to the Ontario Ministry of Health and Long-Term Care.
  • This indicator is not reported as a rate because denominator information about the number of doses of vaccine given is not accurately assessed. Health units would not know the number of doses given in the community by general practitioners and other health care providers.

Cross-References to Other Sections

  • None



Lead Author(s)

Andrea Currie, North York General Hospital
Stephanie Wolfe, Simcoe Muskoka District Health Unit

Contributing Author(s)

Core Indicators Infectious Disease Subgroup

CIWG Reviewers

Core Indicators Infectious Disease Subgroup

External Reviewers

Effie Gournis, Toronto Public Health
Rachel Savage, Ontario Agency for Health Protection and Promotion

Changes Made


Type of Review-Formal Review or Ad Hoc?

Changes made by


March 2009

Formal Review

Infectious Disease subgroup of Core Indicators

  • Changed name from "Adverse Vaccine Events"
  • A new section on Outcomes from the Ontario Public Health Standards was added.

May 11, 2010

Ad hoc

Sherri Deamond on behalf of Infectious Disease subgroup of Core Indicators

  • Removed link to Adverse Vaccine Events Following Immunization - Ontario Definitions and updated with direct link to Appendix B: Provincial Case Definitions for Reportable Diseases of the Ontario Public Health Standards Infectious Diseases Protocol, 2009
Dec 10, 2010Ad hoc

Stephanie Wolfe on behalf of Infectious Disease subgroup of Core Indicators

  • Removed "reported" from indicator description because this implies that reported date is used to assign incidence.  Also added description of dates to use to assign incidence in Analysis Check List.
June 13, 2011Ad hocSherri Deamond on behalf of CIWG
  •  Added acknowledgements section


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