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.
The WHO has published the COVID-19 vaccines: safety surveillance manual to guide the processes for collecting, analysing and sharing safety data and information on COVID-19 vaccines within and across countries. To accompany this manual and facilitate the conduct of active safety surveillance studies using harmonized tools and methods, a protocol template for cohort event monitoring (CEM) studies has been developed. Read more about development of the protocol template, the cohort event monitoring (CEM) study design, and how it can identify previously unrecognised and unsuspected adverse reactions to the vaccine. The CEM protocol was commissioned by World Health Organization (WHO), coordinated by Dr. Christine Guillard with the support of Dr. Noha Iessa, in the Pharmacovigilance (PVG) team, within the Regulation and Prequalification department at WHO Headquarters.
The European Medicines Agency’s safety committee, the Pharmacovigilance Risk Assessment Committee, concluded its preliminary review of a signal of blood clots in people vaccinated with COVID-19 Vaccine AstraZeneca at its extraordinary meeting of 18 March 2021. The Committee confirmed that:
- the benefits of the vaccine in combating the still widespread threat of COVID-19 (which itself results in clotting problems and may be fatal) continue to outweigh the risk of side effects;
- the vaccine is not associated with an increase in the overall risk of blood clots (thromboembolic events) in those who receive it;
- there is no evidence of a problem related to specific batches of the vaccine or to particular manufacturing sites;
- however, the vaccine may be associated with very rare cases of blood clots associated with thrombocytopenia, i.e. low levels of blood platelets (elements in the blood that help it to clot) with or without bleeding, including rare cases of clots in the vessels draining blood from the brain (CVST).
The Vaccine Safety Technical Subgroup of the US CDC’s Advisory Committee on Immunization Practices (ACIP) met on March 1, 2021 to share vaccine safety experience updates and to discuss three sources of vaccine safety monitoring information: Digital apps, Passive surveillance, and the Vaccine Safety Datalink. A video of the one hour long meeting has been posted on YouTube. The updates will be published in the CDC’s Morbidity and Mortality Weekly Report (MMWR) but there’s a great summary of the three sources of vaccine safety monitoring information on the Skeptical Raptor blog, which regularly comments on the science of vaccines.