An Insight Into The Vaccine Causing Blood Clots

On 7 April 2021, the EuropeanMedicines Agency (EMA) officially confirmed that astrazeneca's COVID-19 vaccinehas the potential to cause rare blood clots and thrombocytopenia in people. Asof March 31, 2021, 20 million doses of the vaccine had been administered, and79 people developed blood clots within two weeks of the first dose, mostlywomen under the age of 60. Nineteen of the 79 people died, the organizationsaid. Specific risk factors for thrombosis, such as age, sex, or a history ofprevious clotting disorders, have not been identified.

In a twist, AstraZeneca's vaccineis deeply suspected of thrombosis

In fact, astrazeneca's vaccinecausing blood clots were suspected for a long time. In late February 2021, itwas reported that a small number of healthy people with no previous history ofblood clots developed unusual clotting problems within days of receiving theAstrazeneca vaccine. In march, the reports of astrazeneca vaccine causing bloodclots further expand, some European countries even suspended astrazenecavaccination, but the EMA concluded that there was no conclusive evidence thatthe reported pathology was related to the vaccine, and that the benefits of thevaccine outweighed the risks, so these countries resumed the astrazenecavaccine. AstraZeneca has always held a negative attitude towards this. On March23, AstraZeneca directly announced the Phase III clinical data of the vaccine,again denying the claim that its own vaccine causing blood clots.

An observational analysis of 32,449vaccinated adults in the United States, Peru and Chile found that the vaccinewas 79 percent effective overall and 100 percent effective in preventing severeand hospitalized events. In people over the age of 65, the vaccine is 80percent effective. Although approximately 20% of the subjects were over 65years of age, and 60% of these participants had comorbidities that may increasethe risk of subsequent Novel Coronavirus infection, including diabetes, severeobesity or heart disease, the vaccine demonstrated a good safety record, withno thrombotic related adverse events. AstraZeneca claims that throughout thetrial, the independent data safety monitoring committee found no safety issuesrelated to the vaccine, and that, with the assistance of a neurologist, adeliberate review of thrombotic events and cerebral venous sinus thrombosisduring the trial was conducted. A review of 21,583 participants who received atleast one dose of the vaccine found no instances of the vaccine causing bloodclots or increasing the risk of blood clots.

Preliminary study on the mechanismof thrombosis, similar to heparin-induced thrombocytopenia

The mechanism by which theastrazeneca vaccine causing blood clots is unclear. Some scientists believethat the overactivation of the immune response after the astrazeneca vaccine isthe main cause of the blood clots, because they found antibodies specific toplatelets in the patients. German scientist Andreas Greinacher believes theAstrazeneca vaccine can, in some cases, cause excessive activation of plateletsin the blood, leading to blood clots. They summarised the clinical andexperimental characteristics of nine patients who experienced thrombocytopeniaafter receiving Astrazeneca's COVID-19 vaccine, which the researchers believeis similar to heparin-induced thrombocytopenia (HIT). Heparin is ananticoagulant widely used in clinical practice, but a few patients may haveadverse reactions, namely HIT, with reduced platelet count, thrombosis and skinnecrosis as the main clinical manifestations when receiving heparinanticoagulant therapy. All 9 patients developed thrombosis 4-16 days aftervaccination, with cerebral venous thrombosis in 7 patients, pulmonary embolismin 1 patient, visceral venous thrombosis and cerebral venous thrombosis in 1patient, and death in 4 patients. These patients had not previously beentreated with heparin, but four of them were strongly positive for serum heparinantibody and platelet activation. Platelet activation was not detected in theserum of people who did not develop blood clots after receiving the Astrazeneca vaccine.

Astrazeneca's coronavirus vaccine,which had been highly anticipated but repeatedly thwarted

From the start of clinical trials,the vaccine has repeatedly received negative press. These include previoussuspensions due to volunteer deaths that turned out to be unrelated to thevaccine, conflicting data on protective efficacy due to vaccine dosedifferences, poor response to viral variants, and recent thrombotic events.Even after confirming the link, the EMA said the "benefits outweigh therisks" of taking the vaccine. After all, The Astrazeneca vaccine has beenhigh hopes in the West because it is cheap, easy to transport and store, stableat 2 to 8 degrees Celsius, unlike the harsh temperature conditions of the mRNAvaccine, and friendly to people in remote or poor areas.