Low Risk of Blood Clots and Low Platelet Count for Covid-19 Vaccination-Evidence Based
In today’s Medium article I’ll be focusing on up-to-date information on Thrombosis and Thrombocytopenia, using data from the UK’s MHRA Yellow Card Report. As with any rare side effects that come with any medicine, drugs etc. these side effects can cause doubt and mistrust in a vaccine or other medical product. So without further ado, let’s get into today’s article.
➡️ What is Thrombosis and Thrombocytopenia?
According to Hopkins Medicine — “thrombosis occurs when blood clots block veins or arteries.” [1]
According to Mayo Clinic — “thrombocytopenia is a condition in which you have a low blood platelet count.” [2]
References: [1] https://www.hopkinsmedicine.org/health/conditions-and-diseases/thrombosis#:~:text=Thrombosis%20occurs%20when%20blood%20clots%20block%20veins%20or%20arteries.,a%20stroke%20or%20heart%20attack.
[2] https://www.mayoclinic.org/diseases-conditions/thrombocytopenia/symptoms-causes/syc-20378293
➡️ Information & Studies
A quote from the SPS NHS site says the following: “Thromboembolic events (blood clots) accompanied by thrombocytopenia (low platelets) following administration of the first dose of the AstraZeneca COVID-19 vaccine have been reported. There is currently no evidence of association with the Pfizer-BioNTech or Moderna vaccines. Based on reports to 11 August 2021, the overall incidence following the AstraZeneca vaccine is 14.9 per million first or unknown doses and 1.8 per million-second doses administered. For the latest information please see the weekly summary from the MHRA. “[1]. As we can see from this reliable quote, the overall incidence rate of both Thrombosis and Thrombocytopenia is extremely low and the data from this quote was updated on 9th March 2022.
One study from the NEJM journal looked at 5 patients, all are health care workers aged between 32 to 54 years of age, these 5 cases happened within a vaccinated population of 130,000 people, which indicates Thrombosis and Thrombocytopenia are very rare side effects of the AstraZeneca vaccine [2]. When doing a mathematical percentage based on the numbers from this study, the risk of getting Thrombosis or Thrombocytopenia within this study was 0.003%, this equates to 1 in every 26000 people (based on the data within this study).
A meta-analysis (golden standard of scientific evidence) study that looked at Thromboembolism risk post-Covid-19 infection found that the overall venous TE rate was 21%. [3]
Flights can also carry a risk of blood clotting as well [4], with the information below:
- Flights lasting less than 4 hours — 0.0009%
- Flights lasting over 4 hours — 0.02%
- Flights lasting over 16 hours — 0.08%
When put into context with the study from NEJM a flight lasting over 4 hours one person has an increased risk of getting a blood clot at 0.02% when compared to the NEJM study at 0.003%. In addition to the up-to-date information from the MHRA, the risk of getting blood clots or low-platelet counts is 0.0008% much much LOWER than a flight lasting over 4 hours or a long haul flight over 16 hours.
A study posted in the BMJ on 27th August 2021, which assessed data of more than 29.1million people, found less of a risk with blood clots and low-platelet counts in comparison with SARS-COV-2 infection [5]. This was the conclusion of the BMJ study — “The risks of most of these events were substantially higher and more prolonged after SARS-CoV-2 infection than after vaccination in the same population.”
In the UK about 3,000 to 4,000 of the population have ITP at any one time, again a higher number than reported cases from the MHRA Yellow Card Scheme cases below. [6]
Venous thrombosis, comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), occurs with an incidence of approximately 1 per 1000 annually in adult populations. [7]
The annual incidence of venous thromboembolism is approximately 2 in 1000 of the general population and the annual incidence of diagnosed pulmonary embolism in the UK has been reported as 7–8 per 10,000 people. The risk varies substantially with age; for people under 40 years, the annual incidence of venous thromboembolism is 1 in 10,000, whereas for people over 80 years the incidence rises to 1 in 100. People who have had an episode of venous thromboembolism have a risk of recurrence within 8 years of approximately 30%. However, the risk of recurrence decreases substantially with time and may vary according to the treatment received. [8]
References: [1] https://www.sps.nhs.uk/articles/covid-19-vaccination-and-rare-side-effects-including-blood-clotting/
[2] https://www.nejm.org/doi/full/10.1056/NEJMoa2104882
[3] https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(20)30383-7/fulltext
[4] https://cks.nice.org.uk/topics/dvt-prevention-for-travellers/
[5] https://www.bmj.com/content/374/bmj.n1931
[6] https://www.itpsupport.org.uk/index.php/en/itp-in-adults
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2020806/
[8] https://www.nice.org.uk/guidance/ta287/documents/pulmonary-embolism-acute-treatment-vte-prevention-rivaroxaban-appendix-b-final-scope2
➡️ Current MHRA Data
Data up to 16th March 2022 show that a total of 438 cases of major thromboembolic events (blood clots) with concurrent thrombocytopenia (low platelet counts), (NOTE: this doesn’t make each case a causal event), out of a total of 49,100,000 vaccine doses (1st and 2nd doses) of AstraZeneca. [1]
Breakdown of 438 cases:
- 220 cases occurred in females
- 214 cases occurred in females
- Ages from 18 to 93 years.
The chance of blood clots and low-platelet counts from report cases vs doses administered equates to 0.0008%.
Reported cases equate to 1 in every 112,100 doses.
➡️ Conclusion
There is robust and substantial evidence to state when doing a risk vs benefit analysis of rare side effects such as blood clots and low-platelet count that the benefits of getting the vaccine outweigh the risks. There is more evidence to suggest that post-Covid infection has a greater risk of these events in comparison to vaccination and long haul flights pose more of a risk to someone getting a blood clot or having a low-platelet count than having a Covid-19 related vaccination.
💥 Thanks for reading, Lawrence. Please consider a small contribution, in the form of a beer as all articles are created in my small amount of spare time: https://www.buymeacoffee.com/LawrenceRob