Theo Schetters

Prof dr Veterinary Tropical Diseases

Theo Schetters studied Biology at Utrecht University in the Netherlands. In 1980 he was employed at the Department of Immunology of the Veterinary Faculty of the University of Utrecht where he worked on the antigenic diversity of Trypanosoma parasites. From 1981 to 1987 he worked at the Department of Cytology and Histology at the University of Nijmegen in the Netherlands where he studied immune responsiveness of mice against Plasmodium berghei infection. In 1986 he obtained a PhD in Medicine from Nijmegen University in the Netherlands and received a visiting scientist award from the Royal Society (London) to work on malaria immunology at the National Institute for Medical Research in Mill Hill, London (UK). From 1988 to 2014 he worked at Intervet International (Boxmeer, The Netherlands) where he developed a vaccine against coccidiosis in chickens (Nobilis® Cox ATM) and a vaccine against Babesia infections in dogs (Nobivac® Piro). He is inventor of recombinant vaccines against Babesia divergens and Babesia canis, and an improved vaccine formulation against Rhipicephalus ticks. He is founder of ProtActivity, a company that focuses on vaccine development against protozoal infections. He holds an Extraordinary Professor position at the Department of Veterinary Tropical Diseases, University of Pretoria, Pretoria, South Africa. He is member of the editorial board of Veterinary Parasitology (Elsevier Publishers) and of Parasitology (Cambridge University Press). He has published more than 100 scientific articles (including book chapters) in international scientific journals


The safety and efficacy studies are the core of vaccine development. These require the use of representative product, which means that raw materials used for production, production technology, internal and final product control, the dose of the active ingredient, presentation, and thus the final product, are a close representation of the product for which a marketing authorization is requested. The outbreak of the SARS-CoV-2 virus caused a sense of urgency that initiated a series of changes to formal registration requirements to shorten the time to market. These comprised changes to the use of genetically modified organisms, broad interpretation of what a vaccine is (which allowed skipping of biodistribution studies), in the absence of a validated experimental animal model of COVID-19 allowing immunogenicity studies and in vitro virus neutralization as efficacy studies, compressing phase 1, 2 and 3 studies in humans, and lack of medium and long term safety and efficacy data. As a result, the corona vaccines received an Emergency Use Authorization that allowed the use of the products and required reporting efficacy and safety data obtained from the field. Because it was regarded unethical not to offer vaccine to people that were potentially at risk of severe disease, ongoing registration studies were jeopardized by unblinding and vaccination of the subjects that had received placebo. As a result, only retrospective cohort studies and observational studies can be used to detect possible adverse events. Here we report the temporal association of waves of excess mortality in the population and vaccination campaigns in the Netherlands, and discuss immunopathological mechanisms that could explain these findings.