Different from CVST linked to natural COVID-19 infection
Dr. Coutinho noted that CVST can occur in natural SARS-CoV-2 infection but that vaccine-associated CVST is very different.
“In natural COVID-19 infection, there is an increased risk of thrombosis, and some patients can get CVST as a part of this, but in these cases, this is not accompanied by thrombocytopenia. While the CVST in natural COVID-19 infection is also associated with a bad prognosis, this is more to do with the underlying disease. It is normally the very sick COVID patients who develop CVST, and these patients usually die from the underlying disease rather than the CVST itself,” he explained.
“Clinicians need to be aware of vaccine-related CVST, as it requires very specific and rapid treatment,” Dr. Coutinho stressed.
“Patients presenting with an extremely severe headache (unlike any headache they’ve had before) or with seizures or a focal deficit (weakness in arm or problems with speaking or vision) within 4 weeks of an adenovirus COVID-19 vaccination should ring alarm bells. It is important to do diagnostics quickly, with a platelet count the most important first step, and a rapid CT/MRI scan,” he said.
Other tests that should be conducted are D-dimer for thrombosis and the PF4 antibody test. But results for the PF4 antibody test can take days to come back, and clinicians shouldn’t wait for that, Dr. Coutinho notes.
“Specific treatment needs to be given immediately – with anticoagulation (preferably nonheparin) and immunomodulation with IVIG to stop the immune reaction. Platelets should not be given – that may seem counterintuitive in patients with a low platelet count, but giving platelets makes it worse,” he said.
Is there a geographic difference?
Dr. Coutinho pointed out that fewer cases of this vaccine-related CVST are being reported at the current time.
“We are not sure why this is the case. These adenovirus vaccines are not being used much now in Western countries, but our collaboration covers many less developed countries in South America and Asia, which are relying heavily on these vaccines. We are now shifting focus to these countries, but so far we have only seen a handful of cases from these areas,” he said.
He suggested that this may be because these countries started their vaccination programs later and are vaccinating their elderly (who are not so susceptible to this side effect) first, or it may be because of some environmental or genetic factor that has not yet been discovered.
“This is now an important research question – is the risk of vaccine-induced CVST the same in different countries or ethnicities? This could influence decisions on future vaccine strategies,” Dr. Coutinho said.
“So far, female sex is the strongest risk factor for vaccine-induced CVST. In our cohort, 81% of cases were in women. In addition, 95% were White, but that doesn’t allow us to conclude that this is a risk factor, as the majority of people who have been vaccinated are White. So, we have no clear insight into that yet,” he said.
In a comment for this news organization, the lead author of the previous U.K. report of a series of 70 cases of cerebral venous thrombosis linked to COVID-19 vaccination, Richard Perry, PhD, University College Hospital, London, described this new report as “an excellent study, with many of the same strengths and weaknesses as our study and has very similar results.”
Dr. Perry noted that the two studies used slightly different definitions of vaccine-induced thrombotic thrombocytopenia, but the cases reported appear to be very similar overall. “It is reassuring and gratifying to see that they have made such similar observations,” he said.
“And as they have drawn their cases from a broad range of countries whereas ours were all from the U.K., this provides evidence that the observations from both studies are reasonably generalizable,” he added.
Dr. Perry pointed out that this new report states that TTS occurred in one patient after the patient had received a second dose of the AstraZeneca vaccine. “I would like to know more about this case, because we didn’t see any cases after a second dose in our cohort,” he said.
Dr. Coutinho responded that he didn’t believe this was the first reported case after the second dose.
The study did not receive any specific funding. Dr. Coutinho has received grants paid to his institution from Boehringer Ingelheim and Bayer and payments paid to his institution for data safety monitoring board participation by Bayer.
A version of this article first appeared on Medscape.com.