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Adenoviral vector vaccines

Regulators worldwide reacted to reports of vaccine-induced immune thrombotic thrombocytopenia (VITT) in 2021 with emergency pauses, focused safety reviews, and revised guidance that balanced the rare risk of VITT against the substantial harms of COVID-19.

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Feb 6, 2026

What were the regulatory responses in 2021 to VITT linked to adenoviral COVID‑19 vaccines?

Regulators worldwide reacted to reports of vaccine‑induced immune thrombotic thrombocytopenia () in 2021 with emergency pauses, focused safety reviews, and revised guidance that balanced the rare risk...