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Ask the doctor: Should I be concerned about the Covid vaccine due to a past blood issue when pregnant?


There have been very rare cases of blood clots after people have had the AstraZeneca Covid-19 vaccine

There have been very rare cases of blood clots after people have had the AstraZeneca Covid-19 vaccine

There have been very rare cases of blood clots after people have had the AstraZeneca Covid-19 vaccine

I was on blood thinners for my last pregnancy as I had antiphospholipid syndrome in a previous pregnancy that resulted in miscarriage. I was tested subsequently and told that the issue was pregnancy-related and nothing to worry about outside that. With all the talk of blood clots and the vaccine, should I be concerned about getting it? I am now in my mid 40s.

I think that now the AstraZeneca vaccine is being primarily administered to people age 60-70 only in Ireland, that you are most likely out of any potential danger. The Janssen/ Johnson & Johnson vaccine is similar to the AstraZeneca vaccine in that extremely rare cases of thrombotic events have been observed mainly among females <60 years old typically within two weeks post-vaccination.

Both the Pfizer and Moderna vaccines are manufactured differently based on mRNA technology and they do not have any link to blood clotting events. mRNA refers to genetic material from the virus that causes Covid-19. This genetic material is used in the Pfizer and Moderna vaccine. It gives the body instructions to make a specific piece of protein that is normally found on the virus. In response, the immune system then makes antibodies that can recognise and attack the virus (if exposed) in the future. When you are offered one of these mRNA vaccines, I would strongly encourage you to take it.

Antiphospholipid syndrome (APS) is an auto-immune disease that occurs due to genetic, hormonal and environment factors and makes the affected individual more prone to venous and arterial blood clots. APS occurs when your immune system mistakenly creates antibodies that attack a type of fat cell known as a phospholipid, found in all living cells including blood cells and the lining of blood vessels. Patients present with different signs and symptoms such as blood clots in the heart (causing heart attack), legs, kidneys, brain (causing a stroke) or lungs, recurrent miscarriages, red rash with a lacy net-like pattern, chronic headaches, dementia, and seizures.

Often APS is not diagnosed until a pregnancy-related complication occurs as most people present are aged 20-50 and it is more common in females. Pregnancy is a pro-thrombotic state, making blood clots more common even in healthy individuals.

There is understandably a lot of concern about the risk of clotting with the AstraZeneca and Janssen/Johnson & Johnson vaccine. The most recent data suggests around two to three people per million vaccinated are affected by a blood clot of receiving the first vaccine. The rationale for rolling out this vaccine in the over 60s relates to the risk-benefit ratio which weighs heavily in favour of the vaccination in contrast to the high morbidity and mortality rate associated with Covid-19 in this age group. When one considers the significantly less severe illness caused by Covid-19 in the younger age group, the risk-benefit ratio is not as strong in favour of vaccination.

As things stand, there is emerging data on vaccine-induced-thrombosis with thrombocytopenia and it is felt to be immune-mediated. The only contra-indication to vaccination is previous allergic reaction to Covid-19 or one of the components of the vaccine. A history of thromboembolic (blood clot) disease is not a contraindication to the Covid-19 vaccination.

A precaution to the vaccine is a history of having an immediate allergic reaction to any other (non-Covid 19) vaccine or injectable therapy. In this group of patients and anyone with a history of anaphylaxis due to any cause, the observation time is increased to 30 minutes post Covid-19 vaccination. It is worth noting that the Covid-19 infection is another pro-thrombotic state associated with an increased risk of venous and arterial clotting. The risk is highest in individuals in the intensive care unit, often despite adequate treatment with prophylactic anticoagulation.

If you have any queries, email askthedoctor@independent.ie. Dr Jennifer Grant is a GP with Beacon HealthCheck

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