High index of suspicion required
In a linked commentary, Hugh Markus, PhD, FRCP, professor of stroke medicine at the University of Cambridge, United Kingdom, wrote: “This report emphasizes that the immune mediated coagulopathy can also cause arterial thrombosis, including ischemic stroke, although venous thrombosis and especially cerebral venous sinus thrombosis appear more frequent.
“During the current period of COVID vaccination, a high index of suspicion is required to identify thrombotic episodes following vaccination,” he added. “However, it is important to remember that these side effects are rare and much less common than both cerebral venous thrombosis and ischemic stroke associated with COVID-19 infection itself.”
Several experts who commented on these reports for the Science Media Centre all agreed with Dr. Werring and Dr. Markus that these reports do not alter the current risk/benefit estimates with the vaccine.
, professor of pharmacoepidemiology, London School of Hygiene & Tropical Medicine, who sits on the U.K.’s Medicines and Healthcare Products Regulatory Agency’s Pharmacovigilance Expert Advisory Group, said: “The picture regarding the rare syndrome of blood clots combined with low platelet counts associated with the AstraZeneca vaccine is becoming clearer. Until now, the cases described have tended to involve clots in veins such as cerebral vein thrombosis. In this series of three case reports, we now have some evidence that the types of blood vessels affected include arteries as well as veins.”
“It’s important to stress that such cases remain very rare, and it’s certainly much rarer in people who have had the AstraZeneca vaccine than it is in people affected by COVID-19 itself,” Dr. Douglas emphasized.
“The description of the cases suggests the patients involved presented with the same kind of symptoms as already described in cases involving cerebral vein thrombosis, and they don’t suggest patients need to be on the alert for anything different,” he added.
“However, the emergence of details like this will help guide health professionals who may be faced with similar cases in future; the sooner such cases are recognized, the more chance they will quickly receive the right kind of treatment, hopefully leading to better outcomes.”
, consultant hematologist, University Hospitals Birmingham NHS Foundation Trust, said: “VITT remains a rare complication, and patients with a history of thrombosis, including stroke, should not consider themselves to be at any higher risk of this type of rare thrombosis after vaccination, and COVID infection itself is a significant risk for stroke and other types of thrombosis.”
Many countries have paused use of the AstraZeneca vaccine because of its link to the VITT syndrome or restricted its use to older people as the VITT reaction appears to be slightly more common in younger people. In the United Kingdom, the current recommendation is that individuals under 40 years of age should be offered an alternative to the AstraZeneca vaccine where possible.
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