Covid-19 vaccine: four years later, the list of persistent symptoms is growing

Other very rare vascular/hematologic signals (e.g., other clotting disorders)

What: Small safety signals for rare blood-clotting conditions and related hematologic issues in very large datasets.

Which vaccines: Some signals seen more with adenoviral-vector vaccines, other signals appear across platforms but with low absolute numbers.

How common: Extremely rare, detected only because surveillance datasets included tens of millions of people. PubMed+1

Short interpretation (plain language)
Large-scale surveillance (the GVDN study of ~99 million people) did detect multiple safety signals — e.g., myocarditis/pericarditis (mostly after mRNA vaccines) and GBS/CVT (mostly after adenoviral-vector vaccines). These are real signals that prompted further monitoring and updated guidance. PubMed+1

Absolute risk is small. Even where relative risk increases were detected, the number of excess cases per million doses is usually small (rare events). For most people the benefit of protection from severe COVID-19 outweighs these rare risks. JAMA Network+1

Not all signals equal causation. Surveillance flags associations that require deeper study (case review, clinical adjudication, mechanistic work). Some signals end up clarified as causal in certain subgroups (e.g., myocarditis in young men), others remain uncertain. PubMed+1

Practical advice to include if you’re publishing/sharing this list

Be explicit about rarity. Use absolute-risk language (cases per million) where possible so readers don’t overestimate how common these events are. JAMA Network

Mention which vaccine types most reports involved (mRNA vs adenoviral vector) — that helps readers understand risk patterns. PubMed

Encourage people to seek care if they develop concerning symptoms within a few days–weeks after vaccination (e.g., chest pain, severe headache, leg swelling, new neurologic weakness).

Note benefits too — vaccination reduced hospitalizations and deaths from COVID-19 at a population level; that tradeoff is central to public-health guidance. ScienceDirect