Covid-19 mRNA Vaccines and ITP Explained

Steven Kornweiss, MD covid-19 2 Comments

Featured Image Credit:Photo by James Lee on Unsplash

The American Journal of Hematology published a case report on January 21, 2021 describing the case of a previously healthy 22-year-old male who developed profound thrombocytopenia three days after receiving the Pfizer-BioNTech mRNA vaccine for Covid-19.

This is the first case describing this phenomenon in the medical literature, though the first case was reported by The New York Times, which I covered in my newsletter from January 24. As of today, there are at least twenty-seven similar cases submitted to the Vaccine Adverse Event Reporting System (VAERS).

Today, February 10, 2021, multiple news outlets including Fox News and The New York Times are reporting on this issue with headlines like:

Coronavirus vaccination may be cause of rare blood disorder in at least 36 people: report"


"A Few Covid Vaccine Recipients Developed a Rare Blood Disorder: A link to the vaccines is not certain, and investigations are underway in some reported cases."

What are Platelets?

Platelets are membrane bound cell-like entities that circulate in the blood stream, whose main function is to assist with blood clotting.

In the picture below is a red blood cell (red), white blood cell (blue), and a platelet (yellow).


Under normal circumstances, there are approximately 150,000 to 450,000 platelets in one microliter of blood.

A microliter is 0.0002 teaspoons. Or, in other words, nearly 5,000 micro-liters of blood could fit into one teaspoon. So, a teaspoon of blood contains almost 740 million platelets.

Thrombocytopenia is simply the medical term for "low platelets."

The prefix “thrombo-“ means “relating to the clotting of blood.”

“cyto” means “of a cell or cells.”

And, “-penia” means “a deficiency.”

So, all together, thrombo-cyto-penia means a deficiency of the “cells” that help blood to clot. Strictly speaking, platelets are not cells, but they are cell like.

What Causes Thrombocytopenia?

There are dozens of causes of thrombocytopenia.

One cause is an entity called immune (or idiopathic) thrombocytopenic purpura, or ITP for short.

The term immune means that the condition is mediated by an abnormality of the immune system. Idiopathic means that the exact cause is not known. Thrombocytopenic means that the condition is defined by a low platelet count. And, purpura refers to the primary physical exam finding in this condition, which is a petechial or purpuric rash (see below). Petechiae and purpura are usually caused by the same thing — bleeding within the skin. These rashes are not unique to ITP.

Because these rashes are caused by bleeding within the skin, they are distinguishable from other rashes by their inability to blanch. That is, when you put pressure on one of these lesions, the color cannot be pushed away. The skin does not turn white as it does with many other rashes, because it is impossible to displace the blood which is stuck within the tissue.

Caption: Subtle example of petechiae on the inside of the lower lip

Image attribution: Mdscottis, CC BY-SA 3.0, via Wikimedia Commons


Caption: Less subtle example of purpura on the ankle and leg, with small petechiae on the calf, shin, and just below the knee. You can see this looks very similar to regular bruising, because it’s a similar problem — bleeding within the skin.

Image attribution: See page for author, CC BY 4.0, via Wikimedia Commons

The difference between petechiae and purpura in thrombocytopenia versus regular bruising, is that these rashes occur spontaneously. When platelet levels are extremely low, even regular movement can cause spontaneous bleeding within the skin.

If levels become low enough, spontaneous bleeding can happen within other organs, most notably the brain, which can be catastrophic, and even deadly.

Are mRNA Vaccines for Covid-19 Causing ITP?

It’s still unclear.

According to

The incidence (how many people are diagnosed each year) of ITP among adults in the USA is estimated to be 3.3 per 100,000 adults/year. The prevalence (how many adults have ITP at any time) is 9.5 cases per 100,000.

According to the CDC, roughly 45 million people have been vaccinated as of February 10, 2021 at 0900 ET.

And, after manually reviewing the VAERS data, I found 27 cases with plausible, but unconfirmed reports of thrombocytopenia which could be related to vaccination. I am careful not to say, "caused by vaccination," because coincidence, pre-disposition, and other contributing factors are unknown and likely.

It’s also worth considering that 27 cases out of 45 million is a rate of 0.06 out of every 100,000 people. This is less than one-tenth of the estimated annual incidence.

In other words, the rate at which vaccine recipients are currently developing ITP is lower than you would expect regardless of vaccination. This makes sense that vaccine recipients have a lower incidence of ITP than the general population, as many of the first recipients are young and healthy healthcare workers.

Also, consider that out of the 27 cases I reviewed, it appears that over 20 of them were mild cases. Even most of those that were more severe recovered with treatment (dexamethasone, platelet transfusion, and IVIG).

Critical illness and/or death occurred in three or four cases.

It’s certainly possible that there are more cases yet to be identified or reported, but it’s also possible that many will be attributed to other causes.

Also, consider that thrombocytopenia and even severe ITP has been reported in natural Covid-19 infection as well. This is important context when considering the risks and benefits of vaccination.

The most compelling case linking ITP to Covid-19 mRNA vaccination is the case mentioned at the beginning of this piece. It’s the only case documented in the medical literature thus far.

The facts of the case are as follows:

A 22-year-old otherwise healthy male emergency department employee developed a petechial rash and bleeding of his gums three days after receiving the Pfizer-BioNTech mRNA vaccine. He had no history of these problems. He reported no other symptoms. His vital signs were within normal limits, but on lab examination, two abnormalities were noted. The first, his AST and ALT (liver enzymes), were mildly elevated; the second, his platelets were 2000 per microliter compared to a value of 145,000 per microliter measured just two months prior.

The patient was hospitalized and tested for other infections and autoimmune conditions to search for an alternate diagnosis. None were found, save a single abnormal antibody titer that is usually associated with Sjogren’s disease (an autoimmune disease). However, he did not have other abnormal antibodies or any history of symptoms to suggest a diagnosis of Sjogren’s disease.

He was treated with dexamethasone 40 mg daily for four days, a platelet transfusion, and IVIG at a dose of 1g/kg for two days.

On post-vaccination day six, the patient’s rash and gum bleeding decreased, his platelets count improved to 28,000 and he was able to leave the hospital.

On post-vaccination day eleven, repeat labs demonstrated a normal platelet count of 173,000 and he tested positive for anti-iib/iiia and ia/iia antibodies which is suggestive of ITP.

The author of the study concluded that this case of ITP may have been vaccine related. However, I agree with his broader conclusion:

"Rare vaccination events are important but do not diminish the enormous utility of vaccination and the well-documented safety profile of the Pfizer-BioNTech BNT16B2b2 mRNA vaccine."

Comments 2

  1. Question: Has there been examination of patients with a history of ITP, but no recent instances of the disorder who have had a Covid Vaccination?

    1. Post

      Good question. I haven’t seen such an examination, and I don’t think that VAERS would be helpful to answer this question. And, questioning about a history of ITP is not part of the pre-vaccination screening. So, one would have to conduct a new survey to ask this specific question. I haven’t seen this done yet.

Leave a Reply