What Is the Real Risk of a Central Venous Thrombosis and Portal Vein
Thrombosis in Those Vaccinated With COVID-19 Vaccine?
A preprint published in medRxiv aimed to estimate the absolute risk of central venous thrombosis and portal venous thrombosis in the two weeks following a diagnosis of COVID-19 and to assess the relative risks compared to influenza or the administration of an mRNA vaccine against COVID-19.
The retrospective cohort study used an electronic health records network, which linked records between primary and secondary care centres within 59 healthcare organisations, primarily within the United States.
All patients with a confirmed diagnosis of COVID-19 between January 20th 2020 and March 25th 2021 were included.
This resulted in 537,913 patients being included with a mean age of 46.2, of which 54.9% were females.
Cohorts were matched for age, sex and race with participants diagnosed with influenza or receiving the AstraZeneca or mRNA Pfizer Moderna vaccines as a comparison.
The measured outcome was a diagnosis of central venous thrombosis or portal venous thrombosis within two weeks following the diagnosis of COVID-19.
The incidence of central venous thrombosis after COVID-19 diagnosis was 42.8 per million people, 95%, including 35.3 million 95% first diagnosis.
This was significantly higher than the central venous thrombosis incidence in a matched cohort of patients with influenza and also people who had received an mRNA vaccine.
The incidence of portal venous thrombosis after COVID-19 diagnosis was 392.3 per million people including 175 per million first diagnosis.
This was also significantly higher than portal venous thrombosis incidence in a matched cohort of patients with influenza and people who had received an mRNA vaccine.
The mortality following a central venous thrombosis or portal venous thrombosis was 17.4% and 19.9%, respectively.
The authors concluded that the incidence of CVT and PVT was significantly increased after COVID-19 and the data highlighted the risk of serious thrombotic events in COVID-19 and helped to contextualise the risks and benefits of vaccination within this regard.
The incidence was also many fold higher than the latest reported incidence on CVT following administration of the first dose of the Oxford AstraZeneca vaccine, which the European Medicines Agency have reported to be around 5 per million vaccinated people and the latest reported incidences of CVT following administration of the Johnson and Johnson vaccine. This was reported to be about 0.9 million per vaccinated people.
The authors summarise that COVID-19 was associated with a markedly increased incidence of CVT compared to patients with influenza, people who have received the AstraZeneca or mRNA vaccines and compared to the general population incidence.
The risks with COVID-19 also appeared greater than with the Johnson and Johnson vaccine and the Pfizer vaccine.
The rarity of CVT in all populations means that the larger sample size are required to confirm these results.
Nevertheless, the current data highlighted the risk of serious thrombotic events as a result of COVID-19 infection and helped to contextualise an informed debate about the risk benefit ratio of recurrent COVID-19 vaccines.
The message here is clear that if one is eligible for vaccine and is called, then one should be vaccinated according to current guidelines.
Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed