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The Early Signs of Blood Clots from Vaccination

The Early Signs of Blood Clots from Vaccination

Have you been vaccinated recently? Are you worried that you might experience blood clotting, which the experts now call a “rare” side effect of some vaccines? Here’s what you need to know about the early signs of blood clot from vaccines.

Blood Clotting and COVID-19 Vaccines: What We Know So Far

If you’ve been following news about COVID-19 vaccines, you probably know that two of them, AstraZeneca (now named Vaxzevria) and Janssen (by Johnson & Johnson), are linked to blood clotting incidences.

Janssen is not yet available in the country, but many Filipinos already got the AstraZeneca (AZ) vaccine.

Here’s what we know about the AZ vaccine and blood clotting:

  • Last month, the European Medicines Agency (EMA) stated that “unusual blood clots with low platelets” should be listed as very rare side-effects of AZ.
  • Experts still cannot identify specific risk factors, but most cases occurred in women within two weeks of vaccination.
  • They also observed that blood clots happened in the brain and abdomen.

early signs of blood clots from vaccine

EMA highlighted that the chance of these side-effects occurring is very low. However, one should watch out for the early signs of blood clot from the vaccine so they can seek prompt treatment.

Finally, please note that AZ, Janssen, and the Sputnik vaccine from Russia are all viral vector vaccines. Pfizer and Moderna are mRNA vaccines.

Unusual Blood Clots and Low Platelet Levles: What Do They Mean?

If you’ll notice, experts called the side-effects “unusual.”

This is because blood clotting and low platelet levels don’t typically occur together.

Blood clotting, medically called thrombosis, happens when blood clumps together in the vein or artery. Clotting is helpful when we sustain wounds because it stops bleeding. However, when it occurs within the blood vessel, it could be dangerous. Complications include stroke and heart attack.

On the other hand, platelets help blood form clots. With a low platelet count, blood cannot clump together, and bleeding may happen.

It is extremely rare for a person to have blood clots when they have a low platelet count. Experts call this thrombosis and thrombocytopenia syndrome (TTS) or vaccine-induced prothrombotic immune thrombocytopenia’ (VIPIT).

The Possible Side-Effects of the COVID Vaccine

Early Signs of Blood Clot from Vaccines

Since health agencies are still looking into possible risk factors, they advise the public to watch out for the following early signs of blood clot from vaccines and low platelet count:

  • A headache that worsens when you lie down or bend over
  • A new and severe headache not relieved by usual pain killers or one that worsens
  • Nausea, vomiting, and blurry vision
  • Difficulty with speech
  • Weakness or drowsiness
  • Seizures
  • New and unexplained petechiae, which looks like pinprick bruising or bleeding
  • Shortness of breath
  • Chest pain
  • Leg swelling
  • Persistent abdominal pain

If you experience them within 4 days to 4 weeks of vaccination, seek medical help immediately.

Is It Safe to Get the AstraZeneca Vaccine?

As mentioned earlier, the occurrence of these side effects is extremely rare. EMA also emphasizes that the benefits of getting the vaccine still outweigh the risks.

Recently, the Department of Health also resumed AZ vaccination in all age groups. Recall that the Department temporarily stopped giving it to people aged 60 and below.

The best course of action is to consult your doctor first before a COVID-19 shot, particularly if you have conditions that predispose you to experience blood clotting or low platelet count.

After receiving a shot, watch out for the early signs of blood clot so that you can seek treatment as soon as possible.

COVID Vaccine Second Dose Timing: Why Your Second Dose Is Important

Key Takeaways

When it comes to early signs of blood clot from vaccines, experts believe that blood clotting with low platelet should be listed as an extremely rare side-effect of the AZ vaccine. They haven’t identified specific risk factors yet, but most cases occurred in women within two weeks of vaccination.

If you’ve recently received a vaccine, it’s best to watch out for the early signs of blood clots, so you can get treated as soon as possible.

Learn more about Coronavirus here.

Hello Health Group does not provide medical advice, diagnosis or treatment.


AstraZeneca’s COVID-19 vaccine: EMA finds possible link to very rare cases of unusual blood clots with low blood platelets
Accessed May 25, 2021

The Johnson & Johnson Vaccine and Blood Clots: What You Need to Know
Accessed May 25, 2021

COVID-19 vaccines, thrombocytopenia and blood clots — what’s the story?
Accessed May 25, 2021

COVID-19 vaccination and blood clotting
Accessed May 25, 2021

Accessed May 25, 2021

Guidelines: Diagnosis and Management of Thrombosis with Thrombocytopenia Syndrome (TTS) following Adenovirus Vectored COVID-19 Vaccinations, https://www.un.org/sites/un2.un.org/files/coronavirus_vipitguidance.pdf, Accessed September 14, 2021

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Written by Lorraine Bunag, R.N. Updated Sep 16, 2021
Fact Checked by Vincent Sales