Background

Immune thrombocytopenia, also previously known as idiopathic thrombocytopenia purpura (ITP), is an uncommon autoimmune condition in which the body’s own immune system attacks platelets (the cells found in the blood which normally help the blood to clot). In ITP, the body produces antibodies which attack and destroy platelets, which decreases their number and can cause symptoms such as bruising, pin-point red spots (petechiae) on the skin or bleeding (e.g. nose bleeds or bleeding from the gums). Some people have no symptoms at all.

ITP is most often triggered by a viral illness, occurring in the weeks prior to symptoms developing. ITP can be acute (lasting less than 6 months) or chronic (lasting longer than 6 months), with acute ITP far more common in children and chronic ITP far more common in adults. The symptoms of acute and chronic ITP are the same. Approximately one in every 10,000 child will be affected by ITP.

Some cases of ITP are discovered by chance. In some instances, ITP may go away without any treatment. However, when platelets are very low or there are symptoms of bleeding treatment may be needed. Corticosteroids and intravenous immunoglobulin are the most common forms of initial treatment.

ITP and measles, mumps and rubella vaccines (MMR)

MMR vaccines have been associated with ITP, with the risk estimated at approximately 1 in 25,000 vaccinations.  However, the risk of ITP following MMR vaccine is much lower than the risk seen with natural measles or rubella infections. Patients with a history of ITP are still recommended to receive the MMR vaccine in line with the National Immunisation Program (NIP) as although there is a small risk of relapse, this risk is still present with the viruses themselves, and it is important that people are protected against these viruses which can cause significant morbidity and mortality.

ITP and COVID-19 vaccines

A link between COVID-19 vaccines and ITP is currently being investigated. This is because of the known link between MMR vaccine and ITP, and also because ITP can be triggered by COVID-19 infection. A study in Scotland reported a link between Vaxzevria (AstraZeneca) and ITP, with rates seen post vaccination higher than background rates of ITP in the community . To date, there has been no association found between mRNA COVID-19 vaccines (Comirnaty or Spikevax) and ITP. Monitoring and investigations are and underway in Australia.

Should patients with a history of ITP receive COVID-19 vaccines?

Yes. The effect of COVID-19 vaccination on pre-existing ITP (acute and chronic) has not been well characterised. Limited and early data indicates that vaccination may worsen thrombocytopenia in approximately 10% of patients with chronic ITP post vaccination. However, it is important to note that ITP is most often triggered by a virus, and that the risk of relapse or worsening of ITP is likely higher if these patients contract COVID-19 than the risk following vaccination itself. Patients with a history of ITP are therefore recommended to proceed with vaccination, however, if clinical symptoms worsen post vaccination (days to weeks) then monitoring of platelets and escalation of therapy may be required.

Can patients who develop ITP following the first dose of a COVID-19 vaccine receive dose 2?

Yes. Patients who develop ITP following dose 1 of a COVID-19 vaccines should receive a second dose to complete their course (for two dose vaccine brands) once they are advised that it is safe to do so. Administration of a second dose should be deferred until platelets are stable (>50 x 109/L and off any ITP treatment for >3 months). If a patient remains on immunosuppression (eg. corticosteroids) they should discuss with a heamatologist whether to proceed.

If a patient has ITP following the first dose of Vaxzevria (AstraZeneca), they should receive an mRNA vaccine for their second dose (eg. Comirnaty or Spikevax). If a patient has ITP following the first dose of an mRNA vaccine they should proceed with the second dose of the same vaccine, as no association has been found between mRNA vaccines and ITP to date. There remains a risk of relapse regardless of vaccine brand, however this risk of relapse is higher with COVID-19 disease itself. Close monitoring should occur following vaccination with dose 2 to ensure that there is no further drop in platelets.

ITP and other vaccines

There are some small studies or case reports which suggest a possible increased risk of ITP and other vaccines, such as influenza, HPV, polio and pneumococcal vaccines. However, to date, no vaccines have been proven to be associated with ITP other than the MMR and Vaxzevria (AstraZeneca) vaccines described above. People with a history of ITP are safe to receive all routine NIP and travel vaccines as required.

Resources

 

Authors: Sally Gordon (VicSIS Manager, Department of Health), Paul Monagle (Clinical Haematologist, Royal Children’s Hospital), Francesca Machingaifa (MVEC Education Nurse Coordinator), Rachael McGuire (MVEC Education Nurse Coordinator) and Nigel Crawford (Director SAEFVIC, Murdoch Children’s Research Institute)

Date: August 2021

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.