Vaccinovigilance is a specialized branch of pharmacovigilance focused exclusively on vaccines. The term is widely used, particularly in French-speaking countries and in international health contexts, and it is entirely synonymous with Vaccine Pharmacovigilance.
It encompasses the science and activities relating to the:
- Detection
- Assessment
- Understanding
- Communication
- Prevention
of adverse events following immunization (AEFI) or any other vaccine- or immunization-related issues.
Core Principles of Vaccinovigilance (as detailed in the WHO Manual)
1. It’s a Public Health Imperative
Vaccines are given to healthy individuals, often infants and children, to prevent disease. Therefore, the safety standard demanded is exceptionally high. A robust vaccinovigilance system is crucial to:
- Maintain public trust in immunization programs.
- Ensure that the benefits of vaccines continue to far outweigh the risks.
- Quickly identify and address safety issues before they escalate into crises that can lead to refusal of vaccines and resurgence of diseases.
2. It Uses a Specific Causal Framework for AEFIs
A key aspect of vaccinovigilance is correctly categorizing the cause of an AEFI. The WHO/CIOMS classification is fundamental:
- Vaccine Product-Related Reaction: Caused by the vaccine’s inherent properties (e.g., fever from a live attenuated vaccine).
- Vaccine Quality Defect-Related Reaction: Caused by a manufacturing error (now very rare due to Good Manufacturing Practices).
- Immunization Error-Related Reaction: Caused by a preventable error in handling, storage, or administration (e.g., using a wrong diluent, incorrect injection technique). A primary goal of vaccinovigilance is to identify and correct these errors.
- Immunization Anxiety-Related Reaction: Caused by fear of needles or the injection process (e.g., fainting, hyperventilation).
- Coincidental Event: An illness that happens by chance after vaccination but is not caused by it.
3. It is a Continuous Cycle of Activities
Vaccinovigilance is not just about collecting reports; it is an active, ongoing cycle:
a. Surveillance and Reporting:
- Passive Surveillance: The cornerstone, relying on healthcare providers and sometimes the public to spontaneously report suspected AEFIs.
- Active Surveillance: Proactively monitoring for AEFIs at selected sentinel sites or within specific cohorts, often used for new vaccines.
- Enhanced Surveillance: Used during mass vaccination campaigns to encourage higher reporting rates.
b. Investigation:
- When a serious or unusual AEFI is reported, a detailed investigation is launched. This involves reviewing clinical details, checking vaccine vials and the cold chain, and observing immunization practices.
c. Causality Assessment:
- This is the systematic process to determine the likelihood of a causal link between the vaccine and the event. It is often performed by a national expert committee using standardized algorithms (like the one in the WHO manual) to ensure objectivity and consistency. The outcome is not simply “caused by vaccine” or “not,” but a graded classification.
d. Data Analysis and Signal Detection:
- Collected data is analyzed to calculate reporting rates and compare them to expected background rates of illnesses. This helps distinguish true signals of a potential new adverse reaction from coincidental events.
e. Action and Follow-up:
- Based on the findings, actions are taken. This could be:
- Corrective: Re-training staff, fixing cold chain problems.
- Regulatory: Suspending a faulty vaccine batch, updating product information.
- Clinical: Improving guidelines for managing common reactions.
- Communicative: Informing healthcare professionals and the public.
f. Communication:
- Transparent and timely communication is vital. This involves providing feedback to reporters, informing the public about the findings of investigations, and responding to media inquiries to prevent misinformation.
How it Differs from General Pharmacovigilance
While the principles are the same, the WHO manual highlights key differences that make vaccinovigilance unique:
| Feature | General Pharmacovigilance (for drugs) | Vaccinovigilance |
|---|---|---|
| Target Population | Primarily sick individuals seeking treatment. | Primarily healthy individuals for prevention. |
| Risk Tolerance | Higher, as the drug is used to treat an existing illness. | Extremely low, as the individual is healthy. |
| Scale of Use | Given to a limited number of patients. | Often given to entire populations or cohorts (e.g., all infants). |
| Public Perception | Seen as an individual’s voluntary risk for personal benefit. | Can be seen as an involuntary risk for a communal benefit (herd immunity). |
| Common Events | Coincidental events are less likely to be attributed to the drug. | Coincidental events are very common and often mistakenly attributed to the vaccine, requiring specific expertise to investigate. |
Summary
In essence, vaccinovigilance is the structured, science-based system that ensures the ongoing safety of vaccines from the moment they are licensed through their widespread use in populations. To protect individuals and maintain the integrity of life-saving immunization programs worldwide.
