Ref : https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/astrazeneca-admits-its-covid-vaccine-can-cause-rare-side-effect/articleshow/109710995.cms#

Why in the news?

• AstraZeneca, producer of the Covishield vaccine, has acknowledged the possibility of side effects associated with the inoculation.
• This acknowledgment was made in a legal document submitted to the High Court of Justice in London.
• AstraZeneca’s Covishield can induce Thrombosis with Thrombocytopenia Syndrome (TTS) in extremely rare instances.
• The disclosure highlights the importance of transparency and awareness regarding vaccine safety.

About 

During the Covid-19 pandemic in 2020, a UK-based pharmaceutical company partnered with the University of Oxford to create the AZD1222 vaccine. 

In India, the Serum Institute of India (SII) located in Pune, manufactured and marketed this vaccine under the name Covishield .

AstaZeneca’s Covishield in India 

• In January 2021, the Indian government issued a fact sheet cautioning against administering AstraZeneca’s Covishield to individuals with thrombocytopenia, indicating low platelet counts.
• Vaccination in India began on January 16, 2021.
• Analysis of administered doses revealed a rate of thromboembolic events at 0.61 cases per million doses.
• The Union Health Ministry affirmed that Covishield maintains a favourable benefit-risk balance. The vaccine offers significant potential to curb Covid-19 infections and fatalities.

Observations made by WHO

• WHO noted in April 2021 that cases of Thrombosis with Thrombocytopenia Syndrome (TTS) were reported post-Covishield vaccinations.
• However, the WHO stated that according to the most recent data, the likelihood of TTS occurring with Covishield vaccines seems to be extremely low.

AstraZeneca vaccine in other countries

• In March 2021, several European nations, including France, Germany, Italy, the Netherlands, etc., halted the administration of the AstraZeneca vaccine temporarily following reports of blood clotting incidents.

Thrombosis with Thrombocytopenia Syndrome (TTS) (caused by AstraZeneca’s Covishield)

• Thrombosis with Thrombocytopenia Syndrome (TTS) is a rare condition marked by blood clot formation in blood vessels and a low count of blood platelets.
• This condition is as an exceptionally uncommon adverse reaction linked with specific COVID-19 vaccines. Particularly in the vaccines employing adenovirus vectors, such as AstraZeneca’s Covishield.
• Adenovirus vectors: non-enveloped, double-stranded DNA viruses, commonly used in gene therapy, vaccination, and cancer gene therapy.
• They have high efficiency in delivering genes due to their safety record and ability to express desired genetic material.

Mechanism

• The precise process through which TTS develops post-Covishield vaccination remains unclear.
• One theory suggests that the vaccine might stimulate the immune system, prompting platelet activation and clot formation.
• This mechanism bears resemblance to autoimmune heparin-induced thrombocytopenia,
• Heparin is  a widely used anticoagulant renowned for its ability to prevent blood clotting.

Symptoms

• TTS symptoms encompass breathlessness, chest or limb pain, small red spots or bruising beyond the injection site, headaches, and numbness in body parts.
• TTS can result in blood flow restriction due to clot formation.
• The severity of complications varies depending on the location of the clot. Serious issues may include stroke, heart attack, and severe respiratory difficulties.

Certain factors, including age, gender (with higher prevalence among younger women), and potentially genetic influences, could increase the likelihood of individuals developing this condition.

Statement by AstraZeneca

• AstraZeneca addressed Thrombosis with Thrombocytopenia Syndrome (TTS) in legal papers filed in response to a lawsuit in the United Kingdom.
• The lawsuit pertains to health assertions associated with the vaccine developed by AstraZeneca.
• AstraZeneca denied the claim that TTS is a generic consequence of the vaccine in court documents.
• However, the company acknowledged the potential for TTS to occur as an outcome of its vaccination, but only in exceedingly rare instances.