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What is the rare side effect of AstraZeneca?

Recent revelations regarding a potential rare side effect of AstraZeneca’s COVID-19 vaccine, Covishield, have sparked concerns among the public. A legal submission by AstraZeneca admitted that their vaccine could lead to Thrombosis with Thrombocytopenia Syndrome (TTS), a condition characterised by blood clot formation and low platelet count. However, it’s important to understand the actual risk associated with this side effect.

What is TTS? What are its symptoms?

Thrombosis with Thrombocytopenia Syndrome (TTS) is a severe health condition associated with adenovirus vector vaccines, including Covishield. TTS leads to low platelet count (thrombocytopenia) and the formation of blood clots (thrombosis) within the body. Symptoms of TTS include shortness of breath, chest pain, leg swelling, severe and continuous headaches, stomach aches, and easy bruising.

Do AstraZeneca Covid vaccines cause Thrombosis with Thrombocytopenia Syndrome (TTS)?

Yes, but it is a rare side effect. AstraZeneca has acknowledged a connection between its COVID-19 vaccine, AZD1222, and TTS. The company mentioned in its legal papers that while there is a chance for TTS to occur, it is rare and uncommon. It’s essential to understand that not everyone who receives the AstraZeneca COVID-19 vaccine will be affected by TTS.

The vaccine leaflet by WHO, recently updated in 2022, mentions everything about Vaxzevria, (AstraZeneca Covid vaccines). It also mentions about “Very rare cases of blood clots with low levels of blood platelets have been observed following vaccination with Vaxzevria. The majority of these cases occurred within the first 21 days following vaccination and some cases had a fatal outcome.”

​How much is the risk of developing TTS?

Following the initial dosage of Vaxzevria (AstraZeneca), the estimated risk of developing TTS was 2.6 per 100,000 individuals, with more severe results observed in those under 60 years of age. There was a significantly decreased chance of experiencing TTS after the second dose, as per the Melbourne Vaccine Education Centre.

Is the Covishield-vaccinated population at risk of acquiring TTS?

To a minimal extent. 175 crore doses of Covishield have been given out in India. It is the most widely administered vaccine in India, and there have been a limited number of TTS cases reported across the country, as per The Healthy Indian Project (THIP) which is a member of the WHO-led project. Thrombosis with Thrombocytopenia syndrome (TTS), including vaccine-induced immune thrombotic thrombocytopenia (VITT), is an extremely rare side effect, mostly seen after the initial vaccination. Despite the widespread use of Covishield, other vaccine-induced complications like CVST have not yet been documented in India.

​Should you be concerned if you are vaccinated with Covishield?

No. As of now, there is no reason to panic. Dr Jayadevan, Co-Chairman of the National Indian Medical Association (IMA) Covid Task Force in Kerala, told ANI that TTS is a rare occurrence following specific types of vaccines and other causes. Most cases of TTS are reported within a few weeks of vaccination. Therefore, staying vigilant and consulting a doctor if you experience any symptoms of TTS is advisable.

AstraZeneca developed the COVID-19 vaccine in collaboration with Oxford University. Both vaccines are identical in formulation but are manufactured and distributed in different geographical locations. AstraZeneca’s vaccine is categorised as an adenovirus vector vaccine and has shown 60–80% protection against COVID-19 infection in clinical trials.

It is also to be noted that TTS is linked to other COVID-19 vaccines as well. Johnson & Johnson’s COVID-19 vaccine, named Janssen, has also been associated with this condition. According to a 2023 report by Yale Medicine haematologist Robert Bona, MD, TTS typically occurs in individuals who are bedridden, hospitalised or have other medical issues related to inflammation, infection, or cancer.