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. 2025 May 10;5(1):168.
doi: 10.1038/s43856-025-00891-x.

Comparison of vaccine-induced immune thrombocytopenia and thrombosis cases following two adenovirus-vectored COVID-19 vaccines

Rian Van Rampelbergh  1 , Sue Pavord  2 , Luis Anaya-Velarde  3 , Vitalija van Paassen  4 , Karin Hardt  3 , Emiliano Tatar  5 , Javier Ruiz-Guiñazú  3 , Dawn Baumgardner  5 , Valérie Oriol Mathieu  4 , Nicolas Praet  3 , Hendy Kristyanto  4 , Jerald Sadoff  4 , Macaya Douoguih  4 , Yimei Xu  5 , Frank Struyf  3
Affiliations

Comparison of vaccine-induced immune thrombocytopenia and thrombosis cases following two adenovirus-vectored COVID-19 vaccines

Rian Van Rampelbergh et al. Commun Med (Lond). .

Abstract

Background: Vaccine-induced immune thrombocytopenia and thrombosis (VITT) was first described after administration of adenovirus-vectored COVID-19 vaccines including Ad26.COV2.S and ChAdOx1 nCoV-19. It is not known if the clinical characteristics and outcomes of VITT after Ad26.COV2.S and ChAdOx1 nCoV-19 vaccination are different. We assessed demographic and clinical characteristics, laboratory findings and outcomes in patients with VITT after each vaccine.

Methods: Spontaneous postmarketing reports of VITT after Ad26.COV2.S were identified from Janssen's Global Safety Database and classified using NICE criteria (n = 86). Cases after ChAdOx1 nCoV-19 were identified from a published case series (n = 220). The analysis is descriptive.

Results: The median age of patients with definite/probable VITT after Ad26.COV2.S or ChAdOx1 nCoV-19 vaccination is 43 and 48 years, respectively. Median time-to-onset is 11 days and 14 days post-vaccination, cerebral venous thrombosis (CVT) is present in 50.6% and 50%, and mortality is 30% and 22% of patients, respectively. Women make up 55.3% of cases after Ad26.COV2.S and 55% after ChAdOx1 nCoV-19, 74%/60% of CVT cases and 68%/62.5% of deaths. Patients present with severe thrombocytopenia, grossly elevated D-dimer, and most test positive for anti-platelet factor-4 antibodies. Patients with preexisting rare autoimmune diseases are observed despite the small sample sizes.

Conclusion: Within the limitations of the data, our study finds no strong evidence for a clinically relevant difference in VITT occurring after Ad26.COV2.S or ChAdOx1 nCoV-19. Observed differences in some parameters likely result from the demographic of the populations vaccinated, and the situational and reporting differences in how, when, and where patients were identified and treated.

Plain language summary

VITT (also called Vaccine-induced immune thrombocytopenia and thrombosis) is a rare side-effect that can follow vaccination with certain COVID-19 vaccines (Ad26 and ChAdOx1) and typically presents with blood clots (also called thrombosis) and low levels of platelets (tiny cell fragments that help blood to clot, referred to as thrombocytopenia when low). We investigated the characteristics of patients who developed VITT after vaccination and found no evidence that VITT after Ad26 was different to VITT after ChAdOx1. Both of these vaccines were administered to millions of people and saved many lives during the COVID-19 pandemic. Vaccination continues to be the most effective way to reduce or prevent severe or fatal infections.

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Conflict of interest statement

Competing interests: The authors declare the following competing interests: R.V.R., L.A.V., V.v.P., K.H., E.T., J.R.G., D.B., V.O.M., N.P., H.K. J.S., M.D., Y.X. and F.S. are or were employees of Janssen Research & Development LLC at time of the study and may hold stock or shares in J.&J. S.P. declares no competing interests.

Figures

Fig. 1
Fig. 1. Sequence of events and distribution of VITT cases after Ad26.COV2.S (n = 69) and ChAdOx1 nCoV-19 (n = 205).
Blue arrows refer to activities around Ad26.COV2.S, oange arrows indicate activities around ChAdOx1 nCoV-19. Columns show the number of VITT cases reproted over time for each vaccine. FDA, US Food and Drug Administration; JVCI, United Kingdom Joint Committee on Vaccination and Immunisation; VITT, vaccine-induced immune thrombocytopenia and thrombosis. *Reported during a clinical trial of Ad26.COV2.S
See this image and copyright information in PMC

References

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