Only one young person in a full Wembley Stadium would get blood clot from jab

DECIDING to take up a vaccination is a “balance of risk and benefit”, according to the experts, but the advantages of the Oxford-astrazeneca jab still “far outweigh” any of its risks.

Receiving the Astrazeneca vaccine affords protection against becoming severely ill from Covid-19, and is also likely to reduce transmission.

But the average risk of an adult developing a very rare blood clot is around one in 250,000, according to Dr David Spiegelhalter, a statistician from the University of Cambridge. For older adults the risk is even less, around one in half a million. For people in their 20s it is around one in 100,000, he said.

The Medicines and Healthcare products Regulatory Agency (MHRA), in a press conference with the Joint Committee on Vaccination and Immunisation (JCVI) on Wednesday conceded there is a possibility the jab is causing rare brain blood clots. In light of this, the JCVI has recommended people under-30 should be offered alternative vaccines instead of the Astrazeneca jab.

But what is the risk and how does this compare to others we take in daily life?

“If you vaccinated Wembley Stadium full up with people in their 20s we would certainly expect one to get one of these effects,” Dr Spiegelhalter told BBC Radio 4’s Today programme.

“However, not only (do vaccines) prevent hospitalisations and some intensive care admissions in the others, but think of the prevention of transmission that we would get by vaccinating that many young people.” The risk of dying in a road accident over three months is also one in 100,000 for someone in the 20s, Dr Spiegelhalter added, or in “any sort of accident over the month”.

Statisticians often measure risk using “micromorts” – one micromort represents a one in a million chance of dying.

When using micromorts to understand the risk of dying from other activities and behaviours, the risk of developing a rare blood clot from the Oxford-astrazeneca jab pales in comparison. The risk of dying from a blood clot after receiving the Astrazeneca jab is around one in 1,000,000, the data released by the MHRA so far suggests.

The risk of dying when giving birth is 80 micromorts, around one in 12,500. After having a general anaesthetic your risk is 10 micromorts, a one in 100,000 risk. The chances of being murdered each year are around one in 100,000.