Understanding the Covishield Vaccine and Rare Blood Clot Risk

Written By Center for Vein Restoration
Blog Understanding Covishield

The global COVID-19 pandemic has been an incredibly challenging time for everyone. Thankfully, safe and effective vaccines have helped turn the tide against the virus, and life has returned to pre-pandemic status for most people. However, some concerns have been raised about the potential rare side effects of one particular COVID-19 vaccine made in the United Kingdom and widely used in India. The manufacturer, AstraZeneca, has recently admitted that their vaccine has the rare side effect known as Thrombosis with Thrombocytopenia Syndrome (TTS).

What is Covishield?

Covishield is a viral vector vaccine used to protect against COVID-19. It was developed by the University of Oxford and the British-Swedish company AstraZeneca. The Indian company Serum Institute manufactures the vaccine under the name Covishield.

The vaccine works by using a modified harmless adenovirus as a delivery system. This adenovirus contains instructions for making the SARS-CoV-2 spike protein. After vaccination, your cells produce this spike protein, allowing your immune system to learn to recognize and fight off the actual coronavirus if exposed in the future.

Covishield has been approved for use in many countries worldwide. For maximum effectiveness against COVID-19, two doses given 4-12 weeks apart are required.

Blood Clot Concerns

In March 2021, there were initial reports of rare but serious blood clots occurring in some people after receiving the AstraZeneca/Covishield vaccine. These unusual clots involved low levels of blood platelets and clotting in unusual areas like the brain or abdomen, which can be life-threatening if not promptly treated.

The symptoms of these rare blood clots include severe headache, blurred vision, chest pain, leg swelling, persistent abdominal pain, and shortness of breath. At that time, just over 200 cases of these rare blood clots had been reported out of over 25 million vaccinated people in the UK and Europe. However, the potential connection was concerning enough that many countries paused the use of the vaccine while the cases were reviewed.

According to The Economic Times, AstraZeneca has only recently acknowledged the rare side effect known as Thrombosis with Thrombocytopenia Syndrome (TTS).

Thrombosis is the formation of a blood clot (thrombus) inside a blood vessel, obstructing blood flow. This can lead to serious medical conditions such as heart attack, stroke, deep vein thrombosis, or pulmonary embolism.

Thrombocytopenia syndrome (TTS) is a rare disorder involving low platelet levels (thrombocytopenia) and blood clots (thrombosis) in atypical locations like the brain or abdomen. According to emedicinehealth, symptoms include new, persistent headaches, vomiting, problems with vision, seizures, severe abdominal pain, and deep vein thrombosis.

Center for Vein Restoration (CVR) offers a same-day deep vein thrombosis (DVT) rule-out service or next-day diagnosis and treatment plan options. Our hotline number is 877-SCAN-DVT.

Blood clots caused by COVID-19 vaccines are rare

It's important to note that these blood clots are extremely rare. Additional investigations and real-world data have helped provide some reassurance. Experts now estimate the risk of these rare clots is around 1 in 100,000 doses of the AstraZeneca/Covishield vaccine in younger adults. For most older adults, the risk appears even lower.

It's also important to consider the potential risks in perspective. The dangers of COVID-19 itself, especially for vulnerable groups like the elderly, far outweigh the very small clot risk for most people. Other common medications, like oral birth control pills, actually carry higher blood clot risks.

Covishield Differs from mRNA Vaccines

While Covishield and the Pfizer-BioNTech and Moderna vaccines all work to protect against COVID-19, they utilize different vaccine technologies. Covishield is a viral vector vaccine that uses a modified adenovirus to deliver instructions for making the SARS-CoV-2 spike protein. In contrast, the Pfizer and Moderna vaccines are mRNA vaccines that use messenger RNA encased in lipid nanoparticles to instruct cells to produce the spike protein.

mRNA vaccines represent a truly new vaccine platform, while viral vector vaccines are an adaptation of an existing approach used for other diseases like Ebola. Another key difference is that the mRNA vaccines do not contain any live virus, while Covishield uses a live but modified adenovirus vector. When comparing data across clinical trials, both vaccine types have been shown to be highly effective against COVID-19.

While rare blood clotting issues have only emerged as a potential side effect with viral vector vaccines like Covishield, thrombosis with thrombocytopenia syndrome (TTS) has also been associated with the Johnson & Johnson vaccine, according to Yale Medicine. This is why the Centers for Disease Control and Prevention (CDC) has given preferential recommendations to the Pfizer-BioNTech and Moderna vaccines.

Understanding Blood Clots

Blood clots, also known as thrombi, are gel-like clumps of blood formed from platelets and fibrin proteins that bind together. They normally prevent excessive bleeding by forming a plug that seals off damaged blood vessels. However, certain clots that form inside veins or arteries can be potentially dangerous. These types of clots can block blood flow and cause severe issues like stroke, heart attack, or organ damage.

Blood clots in the deep veins of the legs, known as deep vein thrombosis (DVT), can also break off and travel to the lungs, causing a life-threatening pulmonary embolism (PE). According to the Mayo Clinic, risk factors for developing a DVT blood clot include:

Being over age 60 increases one’s risk. However, anyone at any age can develop a DVT.

Family history
While inherited clotting disorders do not cause blood clots, combined genetics with other risk factors does raise one’s susceptibility to DVT. According to research published in the Archives of Internal titled “The Value of Family History as a Risk Indicator for Venous Thrombosis,” individuals who have a close relative (father or sibling) with a history of DVT were found to have a risk of developing the condition increased by 2.5 times.

Lack of movement
When legs remain stationary for extended periods, the calf muscles responsible for keeping blood circulating can’t fulfill their critical job. Prolonged periods of sitting, such as during long drives or flights, hospitalization, or conditions like paralysis, can also increase the risk of DVT.

The increased pressure on the pelvis and legs caused by pregnancy can last for up to six weeks after birth.

Being overweight
According to a study published by The National Library of Medicine (NIH), obesity increased the risk for venous thromboembolism (VTE) 6.2-fold. Venous thromboembolism includes deep vein thrombosis (DVT) and pulmonary embolism (PE).

The chemicals inhaled from smoking damage the heart and blood vessels, increasing the risk of blood clots, heart attack, and stroke. Even secondhand smoke can cause this damage.

Birth control pills
The hormones in birth control, including pills, patches, and rings, contain estrogen and progestin, or progestin alone. Blood clot formation is primarily associated with estrogen. Talk to your doctor about the safest birth control method for you.

Other health conditions
Heart failure increases blood clot risk, making the symptoms caused by a small pulmonary embolism (PE) more pronounced. Cancer cells release substances that trigger the body to generate a clotting agent.

If you or a loved one have any of these risk factors for DVT blood clots, including having taken the Covishield vaccine, it is vital that you stay vigilant and watch for any signs of deep vein thrombosis.

Center for Vein Restoration (CVR) offers a same-day deep vein thrombosis (DVT) rule-out service or next-day diagnosis and treatment plan options. Our hotline number is 877-SCAN-DVT.

Don’t self-diagnose DVT. Call the Vein Specialists at Center for Vein Restoration

Rely on board-certified vein health professionals to assess your symptoms accurately and guide you on the best course of action. Visit your nearest emergency room or call your Center for Vein Restoration (CVR) vein clinic for timely intervention customized to your needs.

For DVT rule-out services, call CVR at 877-SCAN-DVT.

For all other vein care services, such as the diagnosis and treatment of varicose veins, spider veins, venous ulcers, and the prevention of DVT, call Center for Vein Restoration (CVR). CVR is a nationally recognized leader in treating symptoms of venous insufficiency using outpatient solutions to eliminate unsightly and uncomfortable veins.

Call 240-965-3915 to speak to a Patient Services Representative or schedule your consultation online at a CVR near you today.

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