Issues relating to the safety of the Astra Zeneca vaccine have made the news recently and these may have caused concern to many.
Please be reassured the adverse events that have been observed are VERY rare, but action has been taken to try and minimise risk to patients.
As with any therapy, the risks associated with vaccinations are always considered in light of the benefits. For the vast majority of people, the risks posed by Covid-19 FAR OUTWEIGH the risks attributable to vaccination.
These websites have useful information which explains these risks and benefits in more detail:
Although serious, the adverse effects highlighted yesterday (unusual blood clots) are extremely rare, estimated by the MHRA to be 4 in1,000,000 persons vaccinated in the UK.
To provide some context, the risk of a healthy individual developing a blood clot on a 4+ hour flight is estimated to be 1 in 6000 so You are 42 times more likely to get a clot from the flight than suffer a clot from the AZ vaccine.
The JCVI‘s suggestion to defer the vaccination of healthy 30-year-olds and younger in favour of awaiting a non-AZ option is reasonable given that the current risk posed by Covid to these individuals is LOW.
When the exposure risk posed by Covid becomes HIGH, the risk/benefit of vaccination with the AZ vaccine will change too as illustrated below:
The current advice if for anyone who develops the following symptoms, lasting for 4 or more days after the vaccination, to seek urgent medical attention:
- A new onset of severe persistent headache, blurred vision, confusion or seizures
- Develop shortness of breath,chest pain, leg swelling or peristant abdominal pain
- Unusual skin bruising or pinpoint round spots beyond the injection site
Anyone who has had the first dose of AZ without incident should come forward when called to for their second dose.
Some numbers to think about
Up to and including 31 March 2021, the MHRA had received 79 UK reports of blood clotting cases alongside low levels of platelets (thrombosis associated with thrombocytopenia) following the use of the COVID-19 Vaccine AstraZeneca.
• 44 of the 79 cases were of cerebral venous sinus thrombosis (CVST) with thrombocytopenia
• 35 of the 79 cases were of thrombosis in other major veins (e.g. splenic) with thrombocytopenia
• ALL 79 cases occurred after a FIRST dose of the vaccine
Sadly, 19 people have died out of the 79 cases
• 11 out of the 19 people who died were under the age of 50
• 3 out of the 19 people who died were under the age of 30
The overall risk of such an event, thrombosis associated with thrombocytopenia following a first dose of AZ vaccine, is:
• 4 in a million
• that’s 0.0004 %
The overall risk of death due to that event is:
• 1 in a million
• that’s 0.0001 %
If you’re under 50, the risk of death drops to:
• 1 in 2 million
• that’s 0.00005 %
If you’re under 30, the risk of death drops even further, to:
• 1 in 8 million
• that’s 0.00001 %
To put that into perspective.
The risk of developing a blood clot on an aeroplane flight lasting more than 4hrs is:
▪️ 1 in 6000
▪️ that’s a 167 in a million risk
▪️ or 0.0167%
The risk of developing a blood clot whilst taking the combined oral contraceptive pill is:
▪️ 1 in 2000
▪️ that’s a 500 in a million risk
▪️ or 0.05%
The risk of a DVT or PE developing during pregnancy is:
▪️ 2 in 1000
▪️ that’s a 2000 in a million risk
▪️ or 0.2%
What happens if you develop COVID-19?
• Pulmonary embolism, or clotting on the lungs, occurs in 7.8% of people who have COVID-19
• Deep vein thrombosis (DVT), or clotting in the legs, occurs in 11.2% of people who have COVID-19
• Of those who have COVID-19 and end up in an intensive therapy unit (ITU), 23% will have some form of clot
• COVID-19 causes strokes in 1.6% of people
• Up to 30% of people who have COVID-19 will get thrombocytopenia (a lowering of the platelet count)
The risk of clots and lower platelets, and of course death, is much higher with COVID-19 than these extremely rare events which are occurring with the vaccine.
At the current time (see diagrams above), the risk-benefit ratio for anyone aged 30+ remains overwhelmingly in favour of having the AZ vaccine, as soon as it is offered to you, rather than delaying vaccination (until an alternative one is available AND offered to you) and so running the risk of developing COVID-19 in the meantime – a situation that carries a far, far greater risk of illness and death.
A history of previous venous (DVT/PE) or arterial thrombosis, unless associated with receiving a vaccine, is NOT a contraindication to receiving the AZ vaccine. There are no known (or apparent) risk factors for this very rare event, it appears to be an idiosyncratic immune phenomenon.
