Yet German researchers said these clots appeared more frequently in AstraZeneca-Oxford vaccine recipients than one would expect in people who had never received the vaccine.
What symptoms should doctors and vaccinees look for in the event of an adverse reaction such as blood clots?
European regulators had recommended vaccine recipients to seek medical assistance for a number of possible symptoms, including swelling of the leg, persistent abdominal pain, severe and persistent headache or blurred vision, and tiny spots of blood under the skin beyond the injection site.
But this set of symptoms was so vague that almost immediately UK emergency departments saw an increase in the number of patients who feared they would fit the description. As a result, some emergency department doctors sought more central advice on how to handle what they described as largely unnecessary hospital visits.
German researchers have described specialized blood tests that can be used to diagnose the disorder and suggested treatment with a blood product called intravenous immunoglobulin, which is used to treat various immune disorders.
Medicines called anticoagulants or anticoagulants can also be given, but not a commonly used medicine – heparin – because the disease related to the vaccine is very similar to that which rarely occurs in people receiving heparin.
Do vaccines cause other bleeding disorders?
Other vaccines, especially the one given to children against measles, mumps and rubella, have been linked to a temporary drop in platelet levels, a blood component essential for clotting.
Lowered platelet counts have been reported in a small number of patients receiving Moderna, Pfizer-BioNTech and AstraZeneca vaccines. Recipient, doctor in Florida, has died a brain hemorrhage when his platelet levels could not be restored and others were hospitalized. U.S. health officials have said the cases are under investigation, but have not reported on the results of those exams and have yet to say there is a link to the vaccines.