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Large COVID vaccination study finds thrombosis and thrombocytopenia to be very rare complications

Large COVID vaccination study finds thrombosis and thrombocytopenia to be very rare complications


recently Nature Communications Journal, Researchers determine rate of thrombosis, thrombocytopenia, and thrombocytopenia with thrombocytopenia after vaccination and infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) These rates were compared to background (expected) rates assessed in the UK general population.

Study: Thrombosis and thrombocytopenia after vaccination and infection against SARS-CoV-2 in the UK. Image credit: Rost9 /

study: Thrombosis and thrombocytopenia after vaccination and infection against SARS-CoV-2 in the UK. Image credit: Rost9 /


A collaborative scientific effort has led to the rapid development of a coronavirus disease 2019 (COVID-19) vaccine using several platforms. The most successful are messenger ribonucleic acid (mRNA)-based vaccines. His adenovirus-based ChAdOx1 nCoV-19 and mRNA vaccine, BNT162b2, were subsequently approved for use in the UK on 8 December 2020 and 31 December 2020, respectively. Real data showed that these vaccines were highly effective against his symptomatic COVID-19, severe illness, and hospitalization.

However, rare adverse events such as thrombosis have been reported after vaccination during vaccination programs. As of 26 May 2021, the UK reported a thromboembolic event with thrombocytopenia after primary vaccination with ChAdOx1 nCoV-19 and BNT162b2. Importantly, few BNT162b2 safety concerns have been reported, and cases of immune thrombocytopenia remain rare among BNT162b2 recipients.

About research

In the current study, researchers evaluated six cohorts of individuals from the UK general population to study the effects of COVID-19 vaccination. Her four vaccinated cohorts included individuals who received ChAdOx1 or BNT162b2 vaccines. These individuals received her first or second dose between 8 December 2020 and 2 May 2021 and from the index date he was followed for 28 days.

A fifth cohort consisted of unvaccinated individuals infected with COVID-19 between 1 September 2020 and 2 May 2021, confirmed by reverse transcription-polymerase chain reaction (RT-PCR) testing. it was done. All study participants in this cohort were followed for up to 90 days from initial diagnosis.

A sixth cohort, also referred to as the general population background cohort, included people from the Clinical Practice Research Datalink (CPRD) AURUM as of January 1, 2017. The team followed him up to 31 December 2019 in this cohort.

Study participants aged 20 years or older were included in the primary analysis and provided at least 1 year of previous medical history.

Cerebral venous sinus thrombosis (CVST), pulmonary embolism (PE), visceral vein thrombosis (SVT), deep vein thrombosis (DVT), and combined event venous thromboembolism (VTE), which includes DVT and PE. Two cases of arterial thromboembolism (ATE) were also identified, including myocardial infarction and ischemic stroke.

All cases meeting the Brighton Collaboration definition were considered thrombocytopenic cases. Additionally, platelet counts in patients with thrombocytopenia ranged between 10,000 and 150,000 per microliter. These cases were considered as thrombosis with thrombocytopenic syndrome (TTS) if thrombocytopenia occurred within 10 days before or after thrombosis.

The number of events per 100,000 person-years and the observed coarse incidence rate (IR) were reported with 95% confidence intervals (CI) in addition to absolute risk measures. In addition, standardized incidence rates (SIRs) were calculated at 95% CI by comparing observed and expected rates. All analyzes were stratified by 10-year age group and sex, and by calendar month for the vaccinated group.

Survey results

The study included 401,691 and 9,414,403 SARS-CoV-2-infected individuals and the general public, respectively, plus 3,768,517 and 1,832,841 individuals vaccinated with ChAdOx1 and BNT162b2. The cohort containing the vaccinated population was more female, older, and had a higher prevalence of comorbidities, whereas the SARS-CoV-2-infected population was younger than the general population.

Incidence rate ratio (IRR) for thromboembolic events and thrombocytopenia by age.

After the first dose of ChAdOx1 and BNT162b2, all study cohorts reported an increased risk of VTE with patient age. After the first dose of both ChAdOx1 and BNT162b2, the expected and observed VTE events were 771 and 866, 533 and 595, respectively, with an SIR of 1.12. Conversely, the expected versus observed rate did not increase after his second dose of either vaccine.

Among those who received the first dose of both vaccines, the IRR increased in younger age groups, reaching an IRR of 1 in all age groups in the SARS-CoV-2 RT-PCR positive cohort. This cohort was observed for 1090 and 150 predicted VTEs with an SIR of 7.27.

PE, but not DVT events, resulted in a higher-than-expected VTE incidence after the first dose of ChAdOx1 and BNT162b2. The SARS-CoV-2 RT-PCR cohort had a higher proportion of DVTs as a cause compared to PE events. Additionally, the SIR for PE after positive SARS-CoV-2 RT-PCR was 12.77.

Similarly, observed and expected rates of CVST were higher after the first dose of ChAdOx1 and after SARS-CoV-2 positive RT-PCR testing in 16 vs 4 and 5 vs 1 with SIRs of 4.14 and 3.74, respectively. . The expected rates of SVT versus SARS-CoV-2 RT-PCR test positivity observed were 8 and 3.

Post-vaccination ATE rates were not as high as expected, but increased after a positive SARS-CoV-2 RT-PCR test. Notably, the expected ATE was 134, but increased to 186 after a positive SARS-CoV-2 RT-PCR test. This increased risk was more pronounced between his age of 50 and his age of 79 and was primarily due to the risk of myocardial infarction.

Thrombocytopenia was more common than expected in all study cohorts, with SIRs of 1.27 and 1.47 for the first dose of BNT162b2 and the second dose of ChAdOx1, respectively. The researchers noted more VTE events with thrombocytopenia than ATE.

Observed and expected rates of VTE were higher 16 vs. 12 after the first dose of ChAdOx1, with an SIR CI of 1.38. The incidence of VTE with thrombocytopenia was relatively higher than expected after a positive SARS-CoV-2 RT-PCR test.


Previous studies have reported thrombocytopenia after vaccination against influenza, measles, mumps, and rubella. Case series also suggest that COVID-19 vaccines, especially adenovirus-based vaccines, alone or in combination, increase the risk of thrombosis and thrombocytopenia.

In the current study, researchers observed a similar rate of arterial events among people who received the COVID-19 vaccine. However, further characterization allowed researchers to show that such people were generally older and often had a history of related conditions and medications.

Nonetheless, the benefits of the COVID-19 vaccine outweigh the risks, as all adverse events were rare among vaccinated people.

Journal reference:

  • Burn, E., Li, X., Delmestri, A. and others. (2022). Thrombosis and thrombocytopenia after vaccination and infection against SARS-CoV-2 in the UK.Nature Communications 13(7167). doi:10.1038/s41467-022-34668-w




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