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By Alistair Smout
LONDON, April 15 (Reuters) - There is a much higher risk of
brain blood clots from COVID-19 infection than there is from
vaccines against the disease, British researchers said on
Thursday, after the rollout of inoculations was disrupted by
reports of rare clots.
AstraZeneca and Johnson & Johnson have both
seen very rare reports of cerebral venous sinus thrombosis
(CVST) linked to their vaccines. On Wednesday, the United States
paused vaccinations using J&J's shot while a link with clots was
investigated, with Denmark ditching AstraZeneca's shot over the
issue.
British and European regulators have stressed that the
benefits of vaccination outweigh the risks.
A study of 500,000 COVID-19 patients found CVST had occurred
at a rate of 39 people out of a million following infection,
researchers said. That compares with European Medicines Agency
(EMA) figures showing that 5 in a million people reported CVST
after getting AstraZeneca's shot.
The researchers said in a pre-print study that the risk of
CVST was 8-10 times higher following COVID-19 infection than it
was from existing vaccines for the disease.
"The risk of having a (CVST) after COVID-19 appears to be
substantially and significantly higher than it is after
receiving the Oxford-AstraZeneca vaccine," Maxime Taquet of
Oxford's Department of Psychiatry told reporters.
The study was based on a U.S. health database, and so did
not accrue new data on the risk of clots from AstraZeneca's
vaccine directly, as the shot is not being rolled out there.
Taquet said that the mortality rate from CVST was around 20%
whether it occurred after COVID-19 infection or a vaccine,
indicating the clots were the main risk factor.
Regulators had also observed low platelet levels in reports
of vaccine side effects, but the researchers said data was
limited on whether that was also the case in those reporting
CVST after infection.
The researchers highlighted that COVID-19 was associated
with more common clotting disorders than CVST, such as strokes,
and that recent debate around vaccines had lost sight of how bad
the disease itself could be.
"The importance of this finding is it brings it back to the
fact this is a really horrible illness as a whole variety of
effects including increased risk of (CVST)," John Geddes,
director of NIHR Oxford Health Biomedical Research Centre.
The research team, from Oxford University, said they worked
independently from the Oxford vaccine team which developed
AstraZeneca's shot.
(Reporting by Alistair Smout
Editing by Bernadette Baum)
