An article in the March edition of Vaccine explains why it is necessary to know the background rates of possible Adverse Events of Special Interest (AESI) when monitoring the safety of COVID-19 vaccines. The article provides examples to illustrate the use of background rates and discusses tools available from the Brighton Collaboration that facilitate case evaluation and understanding of AESI.
The Expert Haematology Panel is comprised of UK blood clotting experts, who are meeting daily to collect information on possible cases and are in regular communication with the regulators and other haematology groups studying this potential problem in other European countries. Their guidance includes a link to a living document and the contact details for advice from the Expert Haematology Panel. They state that it is important that correct management is applied to prevent the progression of thrombosis. Of critical note, platelet transfusions should be avoided.
A news item in Nature by Ariana Remmel explains how challenging it is to prove that a medical problem following immunization was caused by the vaccine itself and describes the kinds of studies that are needed to understand the causes of rare adverse events. These include targeted clinical trials and active surveillance systems that collect adverse event data, both background rates and rates after vaccination, from electronic health records.