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May, 2026
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Thom Lysen: Tracking TTS Risk After COVID-19 Viral Vector-Based Vaccines
May 22, 2026, 07:45

Thom Lysen: Tracking TTS Risk After COVID-19 Viral Vector-Based Vaccines

Thom Lysen, Clinical Assessor at Central Committee on Research Involving Human Subjects, shared a post on LinkedIn about a recent article he and his colleagues co-authored, published in Vaccine, adding:

“How do we track safety of COVID-19 vaccines after approval using real-world data?

  • Checking the long-term safety of COVID-19 vaccines presents unique methodological challenges:
  • With high vaccination rates, who is/remains a sensible comparator?
  • Accounting for differences in national rollout.
  • Contextualizing results against evolving risk-minimisation measures, modifying any effects.

Results of the very methodologically thorough post-authorisation safety study of the AZD1222 (AstraZeneca) vaccine to prevent COVID-19 are now published in Vaccine, focused on risk of thrombosis with trombocytopaenia (TTS).

All challenges considered, the totality of evidence suggests a possible increased risk of TTS with post-AZD1222 vaccination that may be higher among subjects less than 60 years and 1–42 days after first AZD1222 dose.

Important insights for AZD1222 recipients and future of viral vector-based vaccines.

Congratulations to the team, including RTI-HS leads Joan Forns, Cristina Rebordosa, former PHARMO colleagues, and the thriving VAC4EU – Vaccine Monitoring Collaboration for Europe.”

Title: Risk of thrombosis with thrombocytopaenia syndrome (TTS) after vaccination with AZD1222: a European VAC4EU post-authorisation safety study

Authors: Joan Forns, Romin Pajouheshnia, Taylor Aurelius, Zachary Bouck, Juan José Carreras, Jungyeon Choi, Albert Cid Royo, Elisa Correcher-Martínez, Silvia Fernandez-Garcia, Catherine Fry, Jordy Gaspersz, Maria Giner-Soriano, Rosa Gini, Anna Girardi, Ron Herings, Wan-Ting Huang, Giulia Hyeraci, Joseph Kim, Samantha Lane, Deborah Layton, Andrew Lee, Thom Lysen, David Martinez, Sima Mohammadi, Denise Morris, Rosa Morros, Dan Ouchi, Jetty Overbeek, Susana Perez-Gutthann, Estel Plana, Robert W. Platt, Giuseppe Roberto, Debabrata Roy, Miriam C.J. Sturkenboom, Amirreza Dehghan Tarazjani, Hae-Won Uh, Arantxa Urchueguía-Fornes, Daniel Weibel, Cristina Rebordosa

Thom Lysen: Tracking TTS Risk After COVID-19 Viral Vector-Based Vaccines

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