Previous research employing data from the CDC’s Vaccine Adverse Event Reporting System database revealed that autoimmune hematologic diseases are rare after immunization for COVID-19, with rates appearing to be lower than those in the general population; however, there have been no studies that have directly compared the occurrence of de novo immune thrombocytopenia (ITP) after receipt of COVID-19 vaccinations with that after other vaccines or COVID-19.

In a recent study published in Cureus, researchers used retrospective deidentified patient data collected from the TriNetX database (Cambridge, Massachusetts), a global federated database that covers over 117 million patients, and sought to investigate the incidence of de novo ITP following administration of mRNA COVID-19 vaccine and to provide a comparative analysis with the incidence following non-mRNA vaccines and COVID-19 infections.

The study involved individuals aged 18 years and older. Additionally, patients were only included if they had at least one healthcare visit prior to the index event. Patients with a history of ITP before the index event were excluded. Those who received other vaccinations or had COVID-19 (except for the COVID-19 group) within 3 weeks of the index event were also excluded.

Four different patient cohorts were included: those who received the mRNA COVID-19 vaccine between December 15, 2020, and May 1, 2023; the influenza vaccine between January 1, 2010, and January 1, 2020; tetanus, diphtheria, and pertussis/tetanus and diphtheria (Tdap/Td) vaccines between January 1, 2010, and January 1, 2020; and those who had COVID-19 between January 1, 2020, and May 1, 2023).

To assess the occurrence of de novo ITP within 3 weeks after receiving mRNA COVID-19 vaccine, non-mRNA vaccines, or upon diagnosis of COVID-19, a comparative analysis was performed. Moreover, a comparative analysis was conducted after a 1:1 propensity score matching to balance baseline characteristics (age, gender, and race).

The results revealed that the overall event rate was 0.07 per 10,000 for the mRNA COVID-19 vaccine, 0.25 per 10,000 for the influenza vaccine, and 0.28 per 10,000 for the Tdap/Td vaccines. Additionally, the incidence of de novo ITP following COVID-19 was 0.30 per 10,000. Individuals who received the influenza vaccine and Tdap/Td vaccines had greater rates of de novo ITP compared with the mRNA COVID-19 vaccine group, with a relative risk of 3.48 and 3.88, respectively. The occurrence of de novo ITP following COVID-19 was notably greater compared with that following the mRNA COVID-19 vaccine, with a relative risk of 4.27, and postpropensity score matching analysis produced comparable outcomes.

Based on their findings, the authors wrote, “Consistent with the literature, this study using real-world data also shows a low incidence of ITP following mRNA-based COVID-19 vaccinations, with an event rate of 0.07 per 10,000 vaccines, albeit higher than the reported data. This is the first study comparing the occurrences of ITP after mRNA COVID-19 vaccines and non-mRNA vaccines, showing a significantly lower rate of ITP following mRNA COVID-19 vaccines compared to other vaccines.”

The authors concluded that this study suggested a significantly lower rate of ITP following mRNA COVID-19 vaccination compared with rates discovered in patients receiving non-mRNA vaccines or those diagnosed with COVID-19.

The authors wrote, “While the incidence of ITP post mRNA COVID-19 vaccination is low, it is higher compared to previous reports. These findings contribute vital evidence to the ongoing discourse on the safety profile of mRNA COVID-19 vaccines. Given the global scale of the COVID-19 vaccination program, continuous monitoring and vigilant reporting of potential side effects remain of utmost importance.”

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