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Covid-19 vaccines and Blood Clots - By Prof. Adrian Newland


Over the last 36 hours a number of countries in Europe have suspended use of the Oxford/Astra Zeneca Covid-19 vaccine following some reports of blood clots in the period following vaccination.  These fall into the category of Deep Vein Thrombosis (DVT) and pulmonary Embolus (PE). They have continued to use the Pfizer vaccine.

From an initial analysis, through the system of recording side-effects (the Yellow Card system in the UK)  there have been 28 reports from the first 10 million Oxford/AZ vaccine and 25 from the first 11 million of the Pfizer vaccine.  from this it is hard to see why the two products have been differentiated.

The two main regulatory bodies, the EMEA (European Medicines Agency) and the MHRA (the Medicines and Healthcare Products Regulatory Agency in the UK) have both confirmed their approval of the vaccines and have not identified blood clots as a problem. The WHO (the World Health Organisation) have said there is no reason to stop using the Oxford/AZ product.

To put blood clots (or thrombosis) into perspective there are about 2,500 recorded in the under 40s each year., which would be around 600 in the last three months.  This incidence ranges from 1 in 10,000 of the under 40 population to as high as 1 in a 100 in the over 80s and, of course, it is in the older age ranges that the vaccines have been concentrated. The averages is about 1 in a 1,000 in the population as a whole.  So far it is in the older age groups that the vaccines have been concentrated and there are additional risk factors that change the risk. These include, in addition to age, obesity, Diabetes, Pregnancy and hormonal treatments such as HRT and the oral contraceptive. 

These figures suggest that we are seeing actually fewer episodes of thrombosis post vaccination than we would expect normally.  This is not to suggest that the vaccination in anyway protects from blood clots but puts the actual problem in perspective.  On the figures so far it is difficult to see why the politicians have made the decision they have, going against expert advice.  This can only delay the rate of vaccination within Europe and has the additional downside of public distrust in the vaccination programme, with its potential consequences.

Professor Adrian Newland  16/03/2021