The U.S. Centers for Disease Control and Prevention’s (CDC) Vaccine Adverse Event Reporting System (VAERS) shows that, as of Jan. 20, 2023, there have been 3,855 cases of pulmonary embolism reported following COVID-19 shots.1 A pulmonary embolism is a blood clot that develops in a blood vessel in the body, often in the leg, and travels to the pulmonary artery in the lungs where it blocks blood flow. This causes lung tissue damage and damage to other organs and can escalate to life threatening conditions and even death.2
Since the COVID pandemic, the incidence of acute pulmonary embolisms has increased. Although it is believed that SARS-CoV-2 infection can cause thrombosis (blood clots), the introduction of COVID shots is also suspected to have increased the risk of unprovoked venous thrombus (blood clot originating in the legs) formation and risk of pulmonary embolism.3
Study Shows Thrombotic Adverse Events Linked to Moderna, Pfizer and AstraZeneca Shots
A 2021 study published in the journal Vaccines was conducted to determine the frequency of reported thrombotic adverse events for three COVID biologics developed by Moderna/NIAID, Pfizer/BioNTech and AstraZeneca/Oxford University, specifically Spikevax, Comirnaty and Vaxzevria.4
An analysis was conducted on reports for the three COVID shots submitted to the EudraVigilance database from Feb. 17 to June 14, 2021. There were a total of 729,496 adverse events out of which 3,420 were thrombotic. 58.1 percent of the thrombosis reports were from Astra Zeneca’s Vaxzevria, followed by 32 percent from Pfizer’s Comirnaty and 9.8 percent from Moderna’s Spikevax.
There were 705 reports of pulmonary embolism for the three shots, of which 18.4 percent were from the Spikevax, 32.1 percent from Comirnaty, and 49.5 percent from Vaxzevria. Sixty-three fatalities were recorded, of which six were related to Spikevax, 25 for Comirnaty, and 32 for Vaxzevria.5
The researchers stated that one of the major limitations of the study is underreporting, over reporting and reporting bias of databases such as EudraVigilance, which makes it challenging to identify the true incidence of these potentially fatal pulmonary embolism events.6
No Solid Evidence Showing High Incidence of Venous Thromboembolism in Post-COVID Patients
Although COVID is widely considered to be a respiratory disease, it has been reported that there is a high incidence of venous thromboembolic complication (blood clot forming in a vein) during SARS-CoV-2 infections.7 However, the true prevalence of thrombosis associated with SARS-CoV-2 infection is unknown since studies to date do not include systematic and comprehensive investigation protocols.8 In additi9on, researchers have had difficulty interpreting the high incidence of pulmonary embolism in critically ill COVID patients because they are by default a high-risk group with multiple comorbidities.9
The medical literature includes some case reports that raise concerns for a potentially increased risk of pulmonary embolism after SARS-CoV-2 infection but researchers say it is still unclear whether pulmonary embolism following SARS-CoV-2 infection is a manifestation of the post-COVID condition or not. A 2022 study published in SN Comprehensive Clinical Medicine found no evidence to prove that a medical history of SARS-CoV-2 infection increases the risk for pulmonary embolism, but that further investigation is needed.10
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1 U.S. Centers for Disease Control and Prevention. The Vaccine Adverse Event Reporting System (VAERS) Results Data current as of 01/20/2023. Jan. 20, 2023.
2 John Hopkins Medicine. Pulmonary Embolism. 2023.
3 Ifeanyi N. et al. Isolated pulmonary embolism following COVID vaccination: 2 case reports and a review of post-acute pulmonary embolism complications and follow-up. Journal of Community Hospital Internal Medicine Perspectives 2021; 11(6): 877-879.
4 Tobaiqy M. et al. Thrombotic Adverse Events Reported for Moderna, Pfizer and Oxford-AstraZeneca COVID-19 Vaccines: Comparison of Occurrence and Clinical Outcomes in the EudraVigilance Database. Vaccines 2021; 9(11): 1326.
7 Mouzarou A. et al. Pulmonary Embolism in Post-CoviD-19 Patients, a Literature Review: Red Flag for Increased Awareness? SN Comprehensive Clinical Medicine 2022; 4(1): 190.
8 Price L. et al. Thrombosis and COVID-19 pneumonia: the clot thickens! European Respiratory Journal 2020; 56(1): 2001608.
9 Mouzarou A. et al. Pulmonary Embolism in Post-CoviD-19 Patients, a Literature Review: Red Flag for Increased Awareness? SN Comprehensive Clinical Medicine 2022; 4(1): 190.