Astrazeneca Vaccine Linked To Rare Blood Clots: An Explainer

Recently, AstraZeneca allegedly confirmed, for the first time in a court document, that its COVID-19 vaccine can lead to a rare side effect called thrombosis with thrombocytopenia syndrome (TTS). What is TTS, and did many people develop this side effect after receiving the AZ vaccine during the pandemic? SJMC Consultant Haematologist Dr Alan Teh provides an explainer on the issue.

"It's not a conspiracy theory; no one is hiding anything. It is a scientific fact we all knew a few years back as with any new drug, clinical trials and research are done to examine the safety and effectiveness. In the case of AZ like other Covid vaccines, it was extensively studied in a large clinical trial involving 30,000 patients and the vaccine was found to be efficacious with no major side effects," Dr Alan said. 

"What we did not know right away was for the side effects to be picked up when used on a larger scale. We may not see any side effects until 100,000 patients are treated and that is considered very rare. In the few million doses administered, very few end up with the side effect which is unfortunate," he stressed. 

Any vaccine side effects would occur between 4 days and 6 weeks, so if you had the vaccine 2-3 years ago, there is nothing to worry about. Dr Alan shares that vaccines are quite transient in the fact that it disappears after a some period of time. However, those with long term side effects leading to severe outcomes, are those who were diagnosed late. 

What is TTS?

Thrombosis is the medical term for blood clot, and thrombocytopenia is the medical term for low platelet, so TTS it is condition where both blood clot and low platelet happens. It is not a specific disease itself. It is a syndrome where these two findings are combined. 

Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT) is a more accurate term for TTS that happens due to a vaccine. This term is preferred to explain a vaccine side effect.

"VITT is quite rare and if it is diagnosed early, it can be treated. However, if it does occur, it is potentially fatal. Yet, only a 20% fatality rate is reported and mostly due to late diagnosis. Now that we know how to diagnose and treat it, a majority of patients will survive," Dr Alan said. 

"I have not personally seen a patient with proven VITT. The public needs to be aware that the Covid infection itself causes blood clots. It is 30 times more common than vaccine related blood clots. Patients with severe Covid who get admitted to ICU are given blood thinners routinely to protect them from blood clots. Incidents of blood clots following Covid infection is 1 in 100, much higher than the vaccine, and that is something we need to put into perspective," he stressed. 

Vaccines are important

We are living in an era where misinformation spreads very fast on social media. "I'd like to remind everyone that we reached a crisis state in pandemic where many were dying from Covid and the health system was almost at a breaking point. What helped to turn the tide was mass vaccination and thankfully, our government secured the vaccine for the population," Dr Alan expressed. 

He believes that viral vaccines are still the mainstay and vaccines where indicated should be still used. For example, the yearly influenza vaccine. Vaccines are an important part of our lives and we shouldn't be afraid of it. 

Source: BFM