Oxford AstraZeneca vaccine update

Oxford AstraZeneca vaccine update

Information about the Oxford AstraZeneca vaccine

Following extensive media coverage the UK’s independent regulator, the Medicines & Healthcare Regulatory Authority (MHRA) issued a detailed statement about the Oxford AstraZeneca Covid vaccine last week.

The MHRA reports that so far there have been 79 cases of venous thromboembolism (VTE) associated with thrombocytopaenia (low platelets) following vaccination with the Oxford AstraZeneca vaccine. Of the cases, 51 were female and 28 were male.

The identified events

44 of the cases had cerebral venous thrombosis and 35 had other type of thrombosis including deep vein thrombosis (DVT), pulmonary embolism (PE) and splanchnic vein thrombosis (which causes persistent abdominal pain.

19 of the cases did not survive and 11 of those who died were under the age of 50. All the cases occurred after the first dose. Although the figures are concerning, they should be viewed in the context of over 20 million vaccination doses having been delivered.

However, there is an age discrepancy with the cases, which is why regulators are responding. Although the overall chance of the vaccine causing a clotting event is 4 in 1 million doses, the majority of the cases occurred in those under 30.

As such, the advice now is that those aged 18-29 should be offered an alternative vaccine where one is available.

Comparison with other vaccines

Although the Oxford AstraZeneca vaccine has been the focus of media coverage, other vaccines can also cause other rare responses.

The Pfizer BioNTech vaccine triggers anaphylaxis at a rate of 5 per 1 million doses. However, there have been no deaths associated with the Pfizer BioNTech vaccine.

Signs and symptoms

The rare responses triggered by the vaccine have an onset usually after 4 days. Those with persistent headache, visual problems, shortness of breath, leg swelling or unexplained bruising or rashes following vaccination should seek medical review.

Although 4 in 1 million patients may experience some kind of clotting event, which means they are incredibly rare, COVID-19 causes blood clots and lower platelet levels at a much higher rate than the Oxford AstraZeneca vaccine.

Comparison with COVID-19

Those with COVID-19 have:

  • a 7.8% chance of developing a pulmonary embolism
  • an 11.2% chance of developing a deep vein thrombosis 

Those admitted to intensive care with COVID-19 have:

  • a 23% chance of a venous thromboembolism
  • 1.6% have a cerebrovascular accident or stroke
  • 30% will develop thrombocytopenia (low platelets)

The risk of clotting and having low platelets is much higher from having COVID-19 than it is from having the Oxford AstraZeneca vaccine (4 in a million is a 0.0004% chance).

Vaccination reduces risks

If you are between 18 and 29 your risk of death and hospitalisation from COVID-19 is lower than those older than you, although getting vaccinated will reduce the risk even further. It also reduces the risk of Long Covid-related complications and reduces the risk of passing COVID-19 onto your loved ones.

Our conclusions and advice

Medical professionals have continued to adapt to the course of the pandemic and continue to build data sets to help make informed decisions. We continue to monitor and review a huge range of clinical information sources and will continue to share updates as more data becomes available.

The Oxford AstraZeneca vaccine remains a safe and effective vaccine and will continue to play an integral role in combating COVID-19. If you have had your first dose of the Oxford AstraZeneca vaccine you should still have your second dose as planned.


13th April 2021

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