10 Suspected Cases of Blood Clot in the Brain Among COVID-19 Vaccinated Individuals


Although the majority of the Singaporean population have gotten vaccinated, there still exist some fears regarding the vaccine and the side effects it could cause.

The safety update on COVID-19 vaccines released by the Health Sciences Authority (HSA) is meant to ease these fears and keep people informed.

HSA Announces 10 Suspected Cases of Blood Clot in the Brain Among Vaccinated Individuals

In its latest safety update on COVID-19 vaccines released on 16 September, HSA announced that there has been 10 suspected cases of cerebral venous thrombosis (CVT) amongst those who have gotten the Pfizer-BioNTech and Moderna COVID-19 vaccines.

According to HSA, “CVT is a very rare type of blood clot occurring in the veins of the brain, which can happen naturally regardless of whether people have been vaccinated. Some of the possible risk factors of CVT include a medical history of blood clotting disorder, head trauma and the use of medicines such as oral contraceptives and hormonal replacement therapies.”

It also stated that the yearly background incidence of CVT in the general population is 1.3 to two per 100,000 persons.

Citing a local study done on the Neurology of COVID-19 in Singapore that was published in the Journal of Neurological Sciences, HSA also stated that “CVT has also been reported to be associated with COVID-19 infection at an incidence of 8.4 per 100,000 infections.”

CVT More Frequent Amongst Asymptomatic Patients

The study, published on 15 November 2020, identified 90 COVID-19 patients with neurological disorders, 39 of which had varying certainty of relationship to COVID-19. Of these 39, four individuals had been identified with CVT.


The study found that CVT occurred relatively early and largely in those with mild infections, with 63.2% being asymptomatic. The study concluded that “CVT was more frequent than expected and occurred in mild/asymptomatic patients.”

Among the 10 suspected reports of CVT, the HSA has reported that none of the cases had been fatal.

However, HSA also stated that it cannot be determined if there is an increased incidence of CVT associated with the use of the mRNA vaccines. The agency explained that this is because “the number of cases of CVT reported is small”, and that there have been “observed fluctuations in the yearly background incidence rates locally.”

Noting that “no overseas regulators have identified CVT as a safety signal with mRNA vaccines” so far, HSA also clarified that “the CVT cases reported locally are not associated with thrombocytopenia (low platelet levels) and are different in clinical presentation from the overseas cases of CVT with thrombocytopenia that has been reported with the AstraZeneca and Janssen (Johnson & Johnson) COVID-19 vaccines.”

That being said, the agency assured that it would continue to monitor this event closely and review the reported cases with its expert panels, as well as update if there are any significant findings.

Read Also: 

Featured Image: Miriam Doerr Martin Frommherz / Shutterstock.com

Fresh grads, you don’t need any experience to earn up to $4,200 with this “secret”:

Read Also: