The definition of vaccination is injecting antigens which can be an intact killed organism or an attenuated organism to induce antibody production in our body. This can help you protect your body from diseases.
Reportedly, some COVID-19 vaccines, especially AstraZeneca and possibly Johnson & Johnson, can cause thrombotic thrombocytopenia which is a blood clotting condition; this condition indicates the low platelet count and is found in some vaccinated people, especially in 30-to-55-year-old females who reside in Scandinavia regions such as Norway and Denmark. Moreover, they are diagnosed with cerebral venous sinus thrombosis. Normally, platelets form clots to stop bleeding; and fibrin, which results from clotting factor, also helps cease the damage of cells or wounds. Heparin is a medication used as an anticoagulant that helps prevent the activity of fibrin. Therefore, this results in the decrease of clotting ability of the blood. However, the platelet count still depends on each individual’s body. AstraZeneca is filled with spike protein of SARS-CoV-2, this spike protein can bind antibody at the binding-site domains as PF4 (platelet factor 4), protein in the body, binds to heparin. This activates the release of antibody from white blood cell and results in blood clotting. Therefore, this increases the possibility of thrombosis. This condition is called vaccine-induced immune thrombotic thrombocytopenia (VITT).
Further research was conducted on antibodies that are secreted without the activation of heparin but are activated by the vaccine instead. The research team takes the serum of patients who have coronavirus along with thrombocytopenia to separate antibodies that bind with PF4. That antibody is also taken to bind with spike protein, and it turns out that they do not bind with each other. This indicates that antibody binding PF4 might not be activated by spike protein from the vaccine like AstraZeneca, but it may result from other unknown factors.
General information of the population who have VITT problems is headache, paralysis, blurred vision, fatigue, and level of platelets less than 150 000 cells per cubic millimetre (thrombocytopenia). VITT is cured by the inhibition of using heparin. However, in cases of healing blood clots, recommended medications are rivaroxaban, apixaban, and edoxaban. We know that blood clots come from vaccination, and the question is, “Should we continue to get vaccines?”
First, we need to consider whether our country has enough types of vaccines for all the people. For instance, in Germany and France, AstraZeneca is used in the first injection, and Pfizer and Moderna are used in the second injection. The second injection is critical because it boosts and multiplies immunity to oppose pathogens that can mutate due to the first injection. In Denmark, AstraZeneca is not allowed, whereas in Thailand we use AstraZeneca. Second, doctors should evaluate the risks and benefits of injecting vaccines. VITT can be found in the elderly or overweight people, so we need to study those cases specifically.
Last but not least, COVID-19 is an emerging infectious disease. The information which we have now will still need to be studied in the future.
References
AstraZeneca’s COVID-19 vaccine: EMA finds possible link to very rare cases of unusual blood clots with low platelets – European Medicines Agency [Internet]. European Medicines Agency. 2021 [cited 16 April 2021]. Available from: https:// www.ema.europa.eu/en/news/astrazenecas-
covid-19-vaccine-ema-finds-possible-link-very- rare-cases-unusual-blood-clots-low-blood
Centers for Disease Control and Prevention. 2021. COVID-19 Vaccination. [online] Available at:
<https://www.cdc.gov/coronavirus/2019-ncov/ vaccines/safety/JJUpdate.html> [Accessed 16 April 2021].
Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination | NEJM [Internet]. New England Journal of Medicine. 2021 [cited 16 April 2021]. Available from: https://www.nejm.org/doi/ full/10.1056/NEJMoa2104840?
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Written by:
Kulisara Singsriwao
Vittavat tangdamrongvong
Thammakan Nampacharoen
AMSA Thailand