UK Yellow Card Scheme
How the MHRA monitors vaccine safety in the United Kingdom.
The Yellow Card Scheme is the UK's flagship system for monitoring the
safety of medicines and vaccines. Run by the Medicines and Healthcare
products Regulatory Agency (MHRA), it has been instrumental in identifying
rare adverse events, particularly during the COVID-19 pandemic.
How the Yellow Card Scheme Works
The Yellow Card Scheme is a voluntary reporting system that allows
healthcare professionals and the public to report suspected adverse drug
reactions:
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Who can report: Healthcare professionals, patients, and
caregivers
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What to report: Suspected reactions to vaccines,
medicines, and medical devices
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Submission methods: Online portal, mobile app, or paper
forms
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Data review: MHRA pharmacovigilance experts analyze
reports continuously
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Regulatory action: Findings can trigger label updates,
safety communications, or product suspensions
Public Access to Data
Unlike some systems, the MHRA provides public access to Yellow Card data:
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Interactive Drug Analysis Profiles: Publicly available
summaries of reports by product
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Weekly COVID-19 reports: Detailed analysis of vaccine
adverse event reports during the pandemic
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Monthly summaries: Regular publications on emerging
safety signals
Key COVID-19 Vaccine Safety Findings
The Yellow Card Scheme played a crucial role in identifying and
quantifying rare adverse events:
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Thrombosis with Thrombocytopenia Syndrome (TTS):
Identified rare blood clots with low platelet counts associated with
Oxford/AstraZeneca vaccine
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Myocarditis/pericarditis: Detected and quantified risk
with mRNA vaccines (Pfizer, Moderna)
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Guillain-Barré Syndrome: Identified increased risk with
Oxford/AstraZeneca vaccine
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Updated guidance: Led to age-based restrictions and
alternative vaccine recommendations
Transparency in Action
The MHRA's decision to publish weekly COVID-19 vaccine safety reports
during the pandemic set an international standard for transparency and
public trust in vaccine safety monitoring.
Yellow Card Data vs. VAERS
Comparing the UK Yellow Card to the US VAERS system:
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More public data: Yellow Card publishes detailed
product-specific analyses; VAERS provides raw data only
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Broader reporter base: UK encourages patient reports,
not just healthcare professionals
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Regulatory context: UK system directly informs MHRA
licensing decisions
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Population coverage: UK has ~67 million population;
VAERS covers entire US
Limitations
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Cannot establish causality — only detects signals for further
investigation
- Subject to underreporting
- Reports contain unverified information
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No denominator data (vaccines administered) for calculating incidence
rates
Sources & Citations