07 / 2025
A research team led by the Paul-Ehrlich-Institut used a preclinical COVID-19 hamster model to examine the efficacy and safety of the first four authorised COVID-19 vaccines – Comirnaty, Spikevax, Jcovden and Vaxzevria. Particular attention was paid to the question of whether there is possible evidence of the development of vaccine-associated enhanced respiratory disease (VAERD). Result: All vaccines protected against severe disease after infection with the original SARS-CoV-2 strain (Wuhan-1) without signs of VAERD. The study was published in the journal NPJ Vaccines.
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Scientists from the divisions of Veterinary Medicine and Safety of Biomedicines and Diagnostics at the Paul-Ehrlich-Institut cooperated on the comprehensive study with colleagues from the Institute of Virology at Phillipps University of Marburg within the framework of the German Center for Infection Research (Deutsches Zentrum für Infektionsforschung, DZIF). Overall coordination was carried out by Dr Michael Mühlebach, Head of the Product Testing Immunological Veterinary Medicinal Products Section at the Paul-Ehrlich-Institut.
One aim of the study was to examine the possibility of developing vaccine-associated enhanced respiratory disease (VAERD) – a subject of intensive public discussion, especially at the beginning of the COVID-19 vaccination campaigns.
A condition known as a vaccine-associated enhanced disease (VAED), which includes VAERD, can be immunologically triggered by two mechanisms: antibody-dependent enhancement (ADE) or vaccine-associated hypersensitivity (VAH). Both processes are associated with a shift in the balance between type 1 and type 2 T helper cell responses, which can influence the release of immunological messenger substances.
The vaccines studied – Comirnaty and Spikevax (mRNA vaccines) and Jcovden and Vaxzevria (adenovirus-based vector vaccines) – protected all animals in the study from severe disease. None of the animals showed clinical or histological signs of VAERD.
As had already been demonstrated in clinical use, the study also showed that mRNA vaccines required a second dose to induce neutralising antibodies, while vector vaccines produced a protective immune response after a single dose.
These results make a significant contribution to the evaluation of the clinical safety and efficacy of the early COVID-19 vaccines and at the same time provide an important impetus for the further development of future vaccines – both against SARS-CoV-2 and against other viral pathogens.
Updated: 21.08.2025
