COVID-19 Vaccines and Rare Blood Clots
Context
- Some COVID-19 vaccines have been linked to dangerous but incredibly rare blood clots.
- Now a small study by researchers’ report in ‘Nature Journal’ is revealing new details on how those clots form.
About
- Vaccine-induced antibodies attach to a protein called platelet factor 4, or PF4, spurring platelets to form clots.
- The vaccine-induced condition is similar to what happens with heparin, a blood thinner that can also attach to PF4.
- When heparin binds to PF4, some people’s immune systems then attack the bound molecules, a condition called heparin-induced thrombocytopenia also characterized by clotting.
- This hints that heparin and COVID-19 vaccines cause blood to clot in similar ways.
Components of Blood
Plasma
- Plasma constitutes 55% of total blood volume. Composed of 90% water, salts, lipids and hormones, it is especially rich in proteins (including its main protein albumin), immunoglobulins, clotting factors and fibrinogen.
- Plasma performs several functions: transporting blood cells and nutrients; regulating the body’s water and mineral salts; irrigating tissues; providing a defence against infections; and coagulating blood.
- Red blood cells, white blood cells and platelets are suspended in plasma.
White Blood Cells
- There are between 6,000 and 8,000 white cells per cubic millimetre of blood.
- White cells, slightly larger than red cells, are also called leukocytes.
- They purify and protect the body from infections.
- Once an infection is detected in any part of the body, the while cells move in to fight it.
Platelets
- Platelets, or thrombocytes, are smaller than the red and white blood cells.
- Platelets play a role in blood coagulation and wound healing.
- When a blood vessel ruptures, platelets combine with fibrin, derived from fibrinogen, to form a clot.
Red Blood Cells
- A drop of blood the size of a pinhead contains approximately 5 million red blood cells (erythrocytes).
- They are small biconcave disks without a nucleus and get their red colour from an iron-containing protein called hemoglobin.
- Red cells make up between 37% and 43% of blood volume in women and between 43% to 49% in men.
- Red blood cells carry oxygen throughout the body.
Antibodies
- Antibodies, also referred to as immunoglobulins, are glycoproteins naturally produced in response to invading foreign particles (antigens) such as microorganisms and viruses.
- They play a critical role in the immune system’s defense against infection and disease.