key: cord-0062005-lfm4o6h3
authors: nan
title: AstraZeneca COVID-19 vaccine: thrombosis with thrombocytopenia
date: 2021-04-17
journal: Reactions Weekly
DOI: 10.1007/s40278-021-94091-4
sha: 4bfaf2c61d74e9f1be177efbaec21d7851135851
doc_id: 62005
cord_uid: lfm4o6h3

nan

The EMA's Pharmacovigilance Risk Assessment Committee (PRAC) concluded on 7 April 2021 that unusual blood clots with low blood platelet levels should be listed as very rare adverse events (AEs) of AstraZeneca COVID-19 vaccine. 2 Most reported cases occurred within 2 weeks after vaccination in women under 60 years of age.

The PRAC carried out an in-depth review of 62 cases of cerebral venous sinus thrombosis (CVST) and 24 cases of splanchnic vein thrombosis (SVT) which were reported in the EU drug safety database EudraVigilance up to 22 March 2021; 18 cases were fatal. "It is thought that the vaccine may trigger an immune response leading to an atypical heparin-induced-thrombocytopenia like disorder," said the EMA. Patients should seek medical attention if they develop symptoms of thrombosis, neurological symptoms including severe persistent headache and/or petechiae beyond the injections site. However, the benefits of the AstraZeneca COVID-19 vaccine continue to outweigh the risks for people who receive it, said the EMA, and it is effective at preventing COVID-19 infections and reducing COVID-19-related hospitalisations and deaths.

The MHRA is not yet recommending age restrictions with regard to use of the AstraAzeneca COVID-19 vaccine; it has reviewed UK reports of very rare specific blood clots with lowered platelet levels and concluded that evidence of a link with the vaccine is stronger but more data are needed. 3 As of 31 March 2021, over 20 million doses of the vaccine had been administered in the UK and the overall risk of these blood clots was 4 cases per million people vaccinated, but the incidence appeared to be slightly higher in younger adults. In total, 79 cases of blood clots alongside low platelet levels were reported in the UK, including 44 cases of CVST with thrombocytopenia and 35 cases of thrombosis in other major veins with thrombocytopenia; 19 of these cases were fatal, including 11 cases in people under 50 years of age. "We thoroughly analyse each and every report as we receive it and although the number of reports of CVST and other thromboembolic events has increased over the last week, so has the overall number of vaccinations administered, therefore these blood clots remain extremely rare and unlikely to occur," said Dr June Raine, MHRA Chief Executive. "The independent Commission on Human Medicines (CHM) and its COVID-19 Expert Working Group together with leading haematologists, has conducted a rigorous scientific analysis of all available evidence regarding reports of thromboembolic events occurring together with low platelets and COVID-19 Vaccine AstraZeneca and usage of the vaccine in different age groups . . . and the MHRA and CHM will continue to keep this under close observation," said Professor Sir Munir Pirmohamed, Chair of the Commission on Human Medicines.

The UK Joint Committee on Vaccination and Immunisation (JCVI) also published a statement on the AstraZeneca COVID-19 vaccine on 7 April 2021, saying that there have been reports of a very rare AE of concurrent thrombosis and thrombocytopenia after the first dose of the vaccine, but no signal for thrombosis/thrombocytopenia after vaccination with other COVID-19 vaccines approved for use in the UK. 4 Available data suggest there may be a trend for an increased incidence of this AE with decreasing age, said the JCVI.

JCVI advises that the benefits of vaccination with the AstraZeneca COVID-19 vaccine far outweigh the risk of AEs in adults 30 years of age and over and those with underlying health conditions putting them at higher risk of severe COVID-19 infection, but advises that it is preferable to offer an alternative COVID-19 vaccine for adults under 30 years of age with no health conditions putting them at higher risk of severe infection.

To date, there are no reports of the very rare thrombosis/thrombocytopenia events following the second dose of the AstraZeneca COVID-19 vaccine, noted the JCVI, and all adults who received a first dose of the vaccine should be offered a second dose of the vaccine irrespective of age. Public Health England is preparing updated information for people being offered COVID-19 vaccines and health professionals, which will be available through the GOV.UK website, commented the JCVI.

The Australian Therapeutic Goods Administration (TGA) has published an updated safety advisory on the risk of thrombosis with thrombocytopenia after vaccination with the AstraZeneca COVID-19 vaccine, saying that as of 9 April 2021, one case of thrombosis with thrombocytopenia reported in Australia has been assessed by the Vaccine Safety Investigation Group (VSIG). 5 The TGA said that an association with gender has not been firmly established, and that the benefit/risk ratio of vaccinating with the AstraZeneca COVID-19 vaccine increases rapidly with increasing age over 50 due to the increase in mortality and life-threatening illness from COVID-19 infection in older people.

The TGA and Australian Technical Advisory Group on Immunisation (ATAGI) are continuing to review all information on thrombosis with thrombocytopenia syndrome (TTS) after administration of this vaccine in Europe, the UK and other countries, as well as Australia. ATAGI recognises this safety concern is likely to have an impact on confidence in the AstraZeneca vaccine in all age groups, and says that until the Australian government can increase supply of other COVID-19 vaccines coverage under Australia's COVID-19 vaccine program will likely be reduced. It says that the AstraZeneca vaccine appears likely to be causally-linked with a risk of TTS, but there is currently uncertainty in the risk rate of this AE.

ATAGI recommends that use of the Pfizer-BioNTech COVID-19 vaccine [Comirnaty] is currently preferred over the AstraZeneca vaccine in adults under 50 years of age who have not received a first dose of AstraZeneca vaccine, but all those who have received their first dose of the AstraZeneca vaccine without any serious adverse effects can be given a second dose of the same vaccine. It supports the government's efforts to procure more or bring forward the delivery of alternate COVID-19 vaccines to replace the use of AstraZeneca COVID-19 vaccine in adults under 50 years of age.

WHO. Interim statement of the COVID-19 subcommittee of the WHO Global Advisory Committee on Vaccine Safety on AstraZeneca COVID-19 vaccine. Internet Document

AstraZeneca's COVID-19 vaccine: EMA finds possible link to very rare cases of unusual blood clots with low blood platelets

MHRA. MHRA issues new advice, concluding a possible link between COVID-19 Vaccine AstraZeneca and extremely rare, unlikely to occur blood clots. Internet Document

Joint Committee on Vaccination and Immunisation. JCVI statement on use of the AstraZeneca COVID-19 vaccine

TGA -Therapeutic Goods Administration. AstraZeneca ChAdOx1-S COVID-19 vaccine Internet Document : 9