Assessing Blood Clot Risks: COVID-19 Vaccination vs. Virus Infection

Assessing the Risk of Blood Clots After the COVID-19 Vaccine

Cases of unusual blood clots have caused concern over the safety of some COVID-19 vaccines. Some fear the vaccine itself could be triggering clots or activating the body’s natural clotting pathways. So is there a real risk of the COVID vaccine causing blood clots?

Read on to learn about the science behind vaccine-related clot concerns. We’ll discuss which vaccines are affected, who’s at risk, and compare clot risks between COVID-19 infection versus vaccination.

Vaccine-Induced Thrombosis and Thrombocytopenia (VITT)

With the Johnson & Johnson and AstraZeneca adenovirus-based COVID-19 vaccines, vaccine-induced immune thrombosis and thrombocytopenia (VITT) has emerged as a very rare potential side effect.

VITT involves widespread blood clotting (thrombosis) accompanied by low blood platelet counts (thrombocytopenia). It occurs about 1–2 weeks after vaccination in around 4–5 people per million vaccinated.

Mechanism Behind Vaccine Blood Clots

These post-vaccination clots seem linked to an over-activation of platelets in the blood. The immune system produces antibodies called platelet factor 4 (PF4) that mistakenly target PF4 bound to platelets.

This leads to excessive platelet activation and clumping. The activated platelets release pro-clotting particles leading to too much clotting. At the same time, the clumping uses up platelets faster than the body replenishes them, resulting in the low platelet count (thrombocytopenia).

Comparing Different Vaccines and Blood Clots

So far, mRNA vaccines like Pfizer and Moderna show no increased VITT risk. However, concern emerged around adenovirus vector vaccines from Johnson & Johnson (J&J) and AstraZeneca.

J&J Vaccine and Blood Clots

In April 2021, six cases of blood clots with low platelets were reported in the US out of 6.8 million doses of J&J vaccine administered. This equals less than one case per million people vaccinated.

A later analysis identified a total of 59 confirmed cases, with nine patient deaths. Overall, this means a less than one in a million chance of developing a serious clot after the J&J shot

AstraZeneca Vaccine and Blood Clots

Initial safety reports also detected rare blood clots following vaccination with the AstraZeneca vaccine, similar to the J&J cases. One study found five cases per million people developed low platelet clots after one AstraZeneca shot.

The AstraZeneca vaccine uses a similar adenovirus vector technology as the Johnson & Johnson vaccine, which may explain why both show (extremely low) VITT risk.

Who's at Risk of Vaccine-Related Blood Clots

Researchers are still trying to determine exact risk factors. But initial data shows:

• Women under age 50 show the highest risk
• Onset occurs about 1-2 weeks after vaccination
• Odds of clots remain extremely low overall

No specific risk factors like medications or health conditions are proven. But anyone experiencing clot-related symptoms in the weeks after vaccination should seek prompt medical care.

Symptoms of Vaccine-Induced Blood Clots

Seek emergency care right away if you develop any of the following 1-3 weeks post vaccination:

• Severe headache that does not respond to over-the-counter pain relievers
• Seizures
• Difficulty moving part of your body or loss of control of movement
• Severe abdominal pain
• Leg swelling
• Petechiae (tiny red spots under skin)
• New or easy bruising

Rapid recognition and treatment is critical for those potentially experiencing VITT.

Weighing Blood Clot Risks: COVID-19 vs Vaccination

While investigating vaccine-related clots remains crucial for safety monitoring, it’s important to frame the risk appropriately.

Some key perspective:

• Less than one in a million people develop a serious clot after J&J or AstraZeneca vaccine
• Twenty times higher risk of blood clots with a COVID-19 infection itself

One study found about 39 VITT cases per million people infected with COVID-19, dramatically higher than the vaccine risk. And COVID-19 related clots prove more deadly, with about one in five patients dying.

So while vaccine blood clots remain an extremely rare event, your odds are still much lower than if going unprotected against the virus itself.

Additional Benefits of Getting Vaccinated

On top of minimizing clot risks from the virus, vaccination provides powerful protection against COVID-19 and its complications like:

• Hospitalization
• Need for intensive care
• Long COVID syndrome
• Organ damage
• Death

The vaccines remain incredibly safe and effective for the vast majority. Evaluating the pros and cons makes vaccination the clear choice to guard individual and public health amid the pandemic.

Take the Safest Vaccine Option For You

If you feel hesitant getting an adenoviral vector vaccine, speak to your doctor about mRNA vaccine options instead. Pfizer and Moderna use mRNA technology shown to have no risk of vaccine-induced clots.

But even with the infinitesimally small clot risk from Johnson & Johnson or AstraZeneca, the benefits still greatly outweigh potential harms for most people.

Vaccination remains a vital public health measure in fighting against the much larger threat of COVID-19. Careful monitoring and prompt treatment of blood clots will help ensure vaccine safety going forward.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.