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Can Vaccines Cause ITP?

ITP is an abbreviation for idiopathic thrombocytopenic purpura.

It is a condition in which our platelets get destroyed, leading to excessive bruising and bleeding, since platelets are needed for normal blood clotting.

What Causes ITP?

To understand what causes ITP, it is important to know it is also often referred to as immune thrombocytopenic purpura, because it is typically the cells of our own immune system that destroys our platelets.


Well, that’s where the idiopathic part comes in.

“In most individuals, however, no such connection to another disease is evident and the cause of anti-platelet antibody production remains unknown.”

Immune Thrombocytopenia

We don’t know why most people develop ITP, although classically, ITP is thought to follow a viral infection, including Epstein-Barr virus (mono), influenza, measles, mumps, rubella, and varicella (chicken pox). ITP has also been associated with many other viral infections, from Dengue fever to Zika.

“Often, the child may have had a virus or viral infection approximately three weeks before developing ITP. It is believed that the body’s immune system, when making antibodies to fight against a virus, “accidentally” also made an antibody that can stick to the platelet cells. The body recognizes any cells with antibodies as foreign cells and destroys them. Doctors think that in people who have ITP, platelets are being destroyed because they have antibodies.”

Pediatric Idiopathic Thrombocytopenia Purpura (ITP)

These children with ITP, usually under age 5 years, develop symptoms a few days to weeks after their viral infections. Fortunately, their platelet counts usually return to normal, even without treatment, within about 2 weeks to 6 months. Treatments are available if a child’s platelet count gets too low though.

“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. The annual prevalence is estimated at 5.3 per 100,000 among children; because children with ITP usually recover, the number of children who have ITP at any one time is almost equal to those diagnosed annually. Worldwide, it is estimated that there are well over 200,000 people affected by ITP. The incidence of ITP increases with age and is more common over the age of 60.”

Immune Thrombocytopenia

Treatments are also available for adults, who also get ITP.

Can Vaccines Cause ITP?

The measles vaccine is the only vaccine that has been clearly associated with ITP, with some studies showing an increased risk 15-35 days after immunization.

“The available data clearly indicate that ITP is very rare and the only vaccine for which there is a demonstrated cause-effect relationship is the measles, mumps and rubella (MMR) vaccine that can occur in 1 to 3 children every 100,000 vaccine doses.”

Cecinati on Vaccine administration and the development of immune thrombocytopenic purpura in children

Even then though, the risk of ITP after a measles containing vaccine, like MMR or ProQuad, is much less than after getting a natural measles infection, so worry about ITP is a not a good reason to skip or delay getting vaccinated.

What about other vaccines?

There is no good evidence that other vaccines, including the chicken pox vaccine, DTaP, hepatitis B vaccine, or flu vaccine, etc., cause ITP.

What about Gardasil? ITP is listed in the package insert as an adverse reaction for Gardasil, but only in the postmarketing experience section, so it does not mean that the vaccine actually caused the reaction, just that someone reported it.

Although ITP is listed in the PI for Gardasil, studies have shown that there is no association.
Although ITP is listed in the PI for Gardasil, studies have shown that there is no association.

Several large studies have actually been done that found no increased risk for ITP after getting vaccinated with Gardasil.

Why might someone report it then?

“Annual incidence rate of ITP was relatively constant; varying slightly between 8.9 per 100,000 (2013) and 12.2 per 100,000 (2012).”

Demonstration of background rates of three conditions of interest for vaccine safety surveillance

They might have coincidentally developed ITP shortly after being vaccinated.

“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.”

Immune Thrombocytopenia

With over 200 million adults in the United States, you can expect that nearly 18 people will get diagnosed with ITP each day. And with hundreds of thousands and soon millions of people getting a COVID-19 vaccine each day, there is a very good chance that these people with ITP will have recently been vaccinated. And of course, that doesn’t mean their vaccine actually caused them to develop ITP.

But how can you know for sure?

Experts will look for safety signals and will make sure that the incidence of ITP and other conditions doesn’t rise above historical rates. For example, if all of a sudden we notice that the incidence of ITP rises to 6 or 9 per 100,000 adults/year after getting a vaccine, then that would be a signal that there could be a problem. A few media reports likely aren’t though.

What to Know About Vaccines and ITP

Although measles containing vaccines can rarely cause ITP, vaccines prevent many more diseases that can cause ITP.

More on Vaccines and ITP

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