Covid-19 is a global pandemic that greatly affected the economic and social conditions of the world. The only solution to the increasing wave of infection is the introduction of vaccines. Many vaccines were administered and put to practical use. However, the AstraZeneca vaccine became a highlight due to reported thrombosis cases after vaccination. Research has shown that it has a role in thrombosis. However, the number of incidents is insignificant and almost negligible. The benefits given by vaccines are far greater than potential harm. The article will cover the reported cases of thrombosis along with blood clotting mechanisms and risk-benefit analysis.
Reported Cases of Thrombosis
In the UK 20.2 million people received doses of the AstraZeneca vaccine. There were 79 reported cases of thrombosis of which only 19 proved fatal.
The risk of thrombosis is 1 in 250,000 people which is 0.000004%. Other risk factors increase the chances of clot formation.
People in the 18-30 age group have more risks of thrombosis compared to older people. Similarly, females are at more risk – 51 out of 79 confirmed cases were women. Low platelet count in the recipient of the vaccine is also a serious concern.
Mechanism Behind Blood Clotting
Blood clotting is a natural body response. It happens due to injury to prevent bleeding and heal the damaged blood vessels.
Platelets are the proteins that are mainly responsible for blood clotting. External or internal bleeding triggers platelet activation for clot formation.
What is VITT
Vaccine-induced immune thrombotic thrombocytopenia (VITT) is the rare side effect of AstraZeneca Covid-19 vaccine. In thrombotic thrombocytopenia, blood clots form in the blood vessels and block blood flow.
Blood clots can be of two types: stationary or embolus. Stationary clots remain fixed in place and block blood flow. On the other hand, embolus blood clots are more dangerous as they move to different organs.
Vaccine Role in Thrombosis
There is an association between thrombosis and AstraZeneca Covid-19 vaccines. The question arises of how vaccines are causing thrombosis.
The vaccine triggers the production of antibodies to protect from future infection. The antibodies produced as a result of the AstraZeneca Covid-19 vaccination are responsible for the activation of platelets.
The antibodies in VITT strongly bind PF4 molecules together forming an immune complex. The immune complex binds to platelets triggering their activation.
The activated platelets undergo a series of reactions to form blood clots in the vessels which can lead to organ failure, stroke, heart arrest, etc.
Risk-Benefit Analysis
Vaccines are available after intensive research, clinical trials, approval by regulatory authorities, and monitoring. Scientific teams and regulatory authorities ensure that vaccines are effective and safe to use.
Despite all efforts, the introduction of new vaccines in the market has some public concerns. The risks posed by vaccines are rare and depend on several factors.
Benefits of Astrazeneca
The benefits of AstraZeneca vaccines outweigh the potential risks.
■ Protect people from long-term COVID and hospitalization
■ Prevent blood clot formation caused by COVID-19
■ A decreasing trend in the number of ICU patients is evident
■ Vaccinated individuals have lifetime vaccine protection
■ Lowers the pathogenicity and virulence of the covid-19
■ Reduces the spread of the disease and allows social interactions
Risk Analysis
Rare instances of thrombotic thrombocytopenia particularly in cerebral venous thrombosis are a major cause of distress.
The overall risk of AstraZeneca-induced cerebral venous thrombosis (CVT) is 5-10 in a million people. The chances of clot formation from COVID-19 are far higher compared to clots caused by AstraZeneca.
Randomized control trials show the safety and efficacy of the vaccine. Published research shows 65-80% and 100% effectiveness in preventing symptomatic and severe cases.
