Challenges in Assessing COVID-19 Vaccines Safety Signals—The Case of ChAdOx1 nCoV-19 Vaccine and Corneal Graft Rejection

The rapid and large-scale roll-out of new COVID-19 vaccines has led to unprecedented challenges in assessing vaccine safety. In 2021, the European Medicines Agency (EMA) processed about 1.7 million safety reports related to COVID-19 vaccines in the EudraVigilance (EV) database and identified more than 900 potential signals. Beyond the large amount of information to be processed, the evaluation of safety signals has faced several difficulties and limitations, both in the assessment of case reports and in the investigation of databases. The evaluation of a signal of corneal graft rejection (CGR) with Vaxzevria^® was no exception to this. In this commentary, we present the challenges encountered in making regulatory decisions in the context of evolving evidence and knowledge. The pandemic crisis emphasised the importance of quick and proactive communication to address the many questions and, above all, to ensure the transparency of safety data.