Risk of blood clots from Covid ten times worse than risk from vaccine


Naturally we all have questions about any new medical procedure and Covid-19 vaccines are no exception.

But widespread vaccination is the only way we will ever get back to normal. Moreover, it is important that nearly everyone gets the jab because if most people are vaccinated the virus cannot spread. 

That is known as herd immunity and is the only way to protect people with defective immune systems.

Australia’s Covid-19 vaccines overall are safe and effective, but there is a tiny risk of people, particularly younger people being affected by blood clots – cerebral venous sinus thrombosis (CVST). 

Yet the risk of clots resulting from an infection is nearly 10 times than that from the vaccine. Research published in The Scientist found a 39 in a million chance of developing CVST due to an infection with Covid-19 and a four in a million chance from vaccination. 

So, the risk of an adverse reaction to the vaccine is small, but much less than not having the vaccine.

To put this risk in perspective, the lifetime risk of dying from a lightning strike in the US is one in 380,000 and the risk of dying from a motor accident is one in 107. There is no comparable Australian data.

Dr Roger Lord, senior lecturer (Medical Sciences) with the Faculty of Health Sciences at the Australian Catholic University said adverse events are rare with 169 cases of CVST and 53 cases of splanchnic vein thrombosis reported from the 34 million people vaccinated in the European Union and UK since April 2021. 

“A higher incidence of the adverse event in younger people, particularly females subsequently prompted Britain’s vaccine advisory board to recommend that the AstraZeneca Covid-19 vaccine not be provided to those under the age of 30.”

In Australia people under 50 may choose to have the Pfizer vaccine, which has not been found to cause blood clots.

Epidemiologist Professor Hassan Vally at La Trobe University says developments regarding the AstraZeneca vaccine and blood clots must be put in perspective. 

“It is certainly a significant setback and one we would prefer we didn’t have to deal with, However, we have to be clear that this is an extremely rare side effect and once again the Australian government has taken an extremely cautious approach to protect our health. 

“In making the adjustments to the vaccine rollout and making Pfizer the preferred vaccine for those under 50 years of age, the goal is to mitigate the risk of this blood clotting syndrome even further, which looks to mainly affect those in the younger age groups.” 

Blood clots have only been found in people after the first shot. If you had no adverse reaction on the first shot, you will be perfectly safe to have the second.

The public health message is clear: Get vaccinated – for your own health and that of your friends and neighbours.

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Frank Smith was trained as an agricultural scientist in the UK, moving to WA in 1974 and shortly afterwards began lecturing at WAIT (now Curtin University) in soils and agronomy. In 1979 he joined the Agriculture Protection Board in charge of publications and media relations, studying part time for a degree in Journalism. In 1992 he spent a year as a visiting professor at the University of Missouri-Columbia. Later he ran a small publication company with his wife Mary-Helen. He then began freelance writing, editing and book indexing. He has written articles for more than 40 magazines in four continents and indexed more than 20 books. In 2007 he started writing for Have a Go News and gradually reduced his writing for other publications. He later took over the subediting, ensuring Have a Go News is consistent in style and highly readable. He and Mary-Helen live in a passive solar home in the Perth Hills with a varying collection of quendas and native birds.