Description

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Context

A study published in a journal has found an association between the inactivated COVID-19 vaccine CoronaVac from Sinovac Biotech and immune thrombotic thrombocytopenic purpura (TTP).

Details

The proposed mechanism involves an autoimmune response that may target ADAMTS13, an enzyme necessary for normal clotting function, but further studies are needed to verify these findings.

An inactivated vaccine is a type of vaccine that uses a virus or bacteria that has been killed or "inactivated" so that it cannot cause disease. These vaccines are designed to help the immune system recognize and fight the virus if it ever encounters it in the future.

What is Thrombotic Thrombocytopenic Purpura?

TTP is a condition where small blood clots form throughout the body’s small blood vessels. These clots can block blood flow to organs like the brain, heart, and kidneys, leading to serious health problems.

When these clots form, they use up the platelets in the blood (platelets help with blood clotting). This means there are fewer platelets left in the bloodstream, which can lead to bleeding and bruising.

Why Does TTP Happen?

TTP is often caused by a problem with an enzyme called ADAMTS13. This enzyme normally prevents clots from forming by breaking down a specific protein in the blood. When ADAMTS13 levels are too low or the enzyme doesn’t work correctly, the blood clots start to form.

Sometimes, TTP occurs because the immune system mistakenly attacks the ADAMTS13 enzyme. This is called an autoimmune reaction, where the body’s immune system attacks its own cells by mistake.

Symptoms of TTP

TTP can cause a variety of symptoms, including:

Feeling very tired or weak.

Easy bruising or bleeding, like nosebleeds, due to low platelet counts.

Known as petechiae, tiny red dots appear on the skin.

Feeling warm or having chills.

Blood clots affecting the brain may lead to headaches, confusion, or even seizures.

How is TTP Treated?

Treatment for TTP needs to start quickly because the condition can worsen fast. Common treatments include:

In Plasma Exchange procedure, plasma (the liquid part of blood) is replaced with plasma from a healthy donor. This helps remove the antibodies attacking ADAMTS13 and adds normal levels of the enzyme to the blood.

Glucocorticoids (Steroids) drugs lower the immune system’s activity, which can help stop it from attacking ADAMTS13.

Rituximab medicine also helps suppress the immune system and can be effective if steroids alone aren’t enough.

Sources:

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PRACTICE QUESTION

Q.Which of the following statements about the inactivated vaccines are correct?

Inactivated vaccines use pathogens that are killed through chemical or physical processes to stimulate an immune response.
Inactivated vaccines generally require booster doses to maintain immunity over time.
Inactivated vaccines can replicate within the host and therefore provide long-lasting immunity similar to live-attenuated vaccines.

Select the correct answer using the codes given below:

(a) 1 and 2 only

(b) 2 and 3 only

(d) 1, 2, and 3

Answer: (a)

Explanation:

Statement 1 is correct. Inactivated vaccines contain pathogens (viruses or bacteria) that have been killed or inactivated, typically through chemical or physical methods, to prevent them from causing disease while still eliciting an immune response.

Statement 2 is correct. Since inactivated vaccines do not replicate in the host, they generally produce a weaker immune response than live-attenuated vaccines. As a result, multiple doses or booster doses are often required to maintain immunity.

Statement 3 is incorrect. Inactivated vaccines do not replicate within the host. Unlike live-attenuated vaccines, which contain weakened but live pathogens that can replicate and create a more robust immune response, inactivated vaccines cannot replicate, and thus the immunity they provide tends to be less durable and requires boosters.