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.