02 May 2024 Covishield causes Thrombosis with thrombocytopenia syndrome
This article covers ‘Daily Current Affairs’ and the topic details of ”Covishield causes Thrombosis with thrombocytopenia syndrome”. This topic is relevant in the “Science and Technology” section of the UPSC CSE exam.
Why in the News?
AstraZeneca, the manufacturer of the AZD1222 vaccine, branded as Covishield in India, has recognised a possible connection between its vaccine and Thrombosis with Thrombocytopenia Syndrome (TTS), an uncommon condition marked by decreased platelet levels and the formation of blood clots.
More about the News
- The acknowledgement was made in a legal document submitted to the High Court in London, where AstraZeneca admitted that the vaccine “can, in very rare cases, cause TTS.” TTS typically presents with symptoms such as severe headaches, abdominal pain, leg swelling, shortness of breath, and neurological deficits. The consequences of TTS can be severe, including strokes, brain damage, heart attacks, pulmonary embolism, and even amputation.
- Medical professionals in India have highlighted that this information is not new, as the potential for TTS has been included in the product information for the Covishield vaccine since its introduction in the country.
- Medical professionals have also emphasised that COVID-19 itself increases the risk of clotting, heart attacks, and strokes, both during and after recovery. While TTS is a real risk, it is considered extremely rare. Most TTS events occur within the first 21 days following vaccination, and unfortunately, some cases have resulted in fatalities.
- Despite these risks, doctors advise against panic, as the Covishield vaccine has proven effective in protecting millions of people from severe COVID-19 infection. Patients who have received the Covishield vaccine are advised to stay vigilant and consult a doctor if they experience any symptoms of TTS, such as severe headaches, abdominal pain, or leg swelling. Timely recognition and management are crucial for improving outcomes in individuals affected by this rare but serious syndrome.
About Covishield
- Covishield is a vaccine developed to combat the Covid-19 pandemic. It is based on the AZD1222 vaccine, which was developed through a collaboration between a UK pharmaceutical company and the University of Oxford in 2020. In India, Covishield is produced by AstraZeneca and manufactured by the Serum Institute of India (SII) located in Pune.
- The Indian government issued a fact sheet in January 2021 cautioning about the administration of Covishield to individuals with thrombocytopenia, a condition characterised by low platelet counts. Vaccination efforts in India began on January 16, 2021, aiming to curb the spread of Covid-19.
- Despite initial concerns, the Union Health Ministry in India has emphasised the significant benefits of Covishield in reducing COVID-19 infections and related deaths. The vaccine has been instrumental in the global fight against the pandemic.
- However, like other vaccines, Covishield has faced scrutiny in some countries. In March 2021, several European nations temporarily halted the use of the AstraZeneca vaccine, including Covishield, due to reports of blood clotting incidents.
- Subsequent observations by the World Health Organization (WHO) in 2021 noted cases of Thrombosis with Thrombocytopenia Syndrome (TTS) occurring after Covishield vaccinations. However, the WHO has stated that based on available data, the risk of TTS associated with Covishield vaccines appears to be very low.
What is Thrombosis with thrombocytopenia syndrome?
Thrombosis with thrombocytopenia syndrome (TTS) is an infrequent yet severe medical condition characterised by abnormal blood clotting (thrombosis) and reduced platelet counts (thrombocytopenia).
Causes
- Vaccine-Induced: TTS has primarily been linked to adenovirus vector-based COVID-19 vaccines like AstraZeneca and Johnson & Johnson. It is thought to arise from an immune reaction prompted by the vaccine, leading to platelet activation and clot formation.
- Other Triggers: TTS may also occur due to factors such as specific medications, infections, or autoimmune disorders, though these instances are less common.
Symptoms
- Blood Clots: Individuals with TTS might develop blood clots in various body parts, including deep vein thrombosis (DVT), pulmonary embolism (PE), cerebral venous sinus thrombosis (CVST), and arterial thrombosis.
- Thrombocytopenia: Reduced platelet counts are a key characteristic of TTS and may manifest as easy bruising, petechiae (small red or purple spots on the skin), or prolonged bleeding from minor injuries.
- Other Symptoms: Patients may also experience general symptoms like fatigue, weakness, shortness of breath, and abdominal discomfort.
Diagnosis:
- Physicians evaluate patients for signs and symptoms suggestive of TTS, including recent vaccination history or other potential triggers.
- Blood tests are performed to assess platelet counts, coagulation parameters (such as D-dimer levels), and the presence of antibodies linked to TTS.
- Imaging techniques such as ultrasound, CT scans, or MRI may be utilised to visualise blood clots and evaluate their location and severity.
Treatment:
- Anticoagulant medications such as heparin or direct oral anticoagulants (DOACs) are commonly prescribed to prevent clot progression and lower complication risks.
- In severe cases of thrombocytopenia or active bleeding, platelet transfusions may be necessary to restore platelet counts and manage bleeding.
- For individuals with vaccine-induced TTS, certain immunomodulatory therapies like intravenous immunoglobulin (IVIG) or corticosteroids may be beneficial in suppressing abnormal immune responses.
Different vaccines for Covid and their working
Various COVID-19 vaccines have been developed to combat the global pandemic caused by the novel coronavirus, each utilising different mechanisms to provide immunity. Here’s an overview of some of these vaccines and how they work:
mRNA Vaccines (e.g., Pfizer-BioNTech, Moderna)
- mRNA vaccines contain genetic material called messenger RNA (mRNA), which encodes a portion of the spike protein found on the surface of the SARS-CoV-2 virus.
- Once injected into the body, the mRNA enters cells and instructs them to produce the spike protein.
- The immune system recognises the spike protein as foreign and mounts an immune response by producing antibodies and activating T cells.
- If the vaccinated individual later encounters the actual virus, their immune system is primed to recognise and neutralise it, preventing infection.
Viral Vector Vaccines (e.g., AstraZeneca, Johnson & Johnson)
- Viral vector vaccines use a harmless virus, such as an adenovirus, as a vector to deliver genetic material from the SARS-CoV-2 virus into cells.
- The genetic material carried by the viral vector instructs cells to produce the spike protein.
- Similar to mRNA vaccines, the immune system recognises the spike protein and mounts an immune response, generating antibodies and T cells.
- Upon subsequent exposure to the virus, the immune system is prepared to respond rapidly and effectively, providing protection against infection.
Protein Subunit Vaccines (e.g., Novavax)
- Protein subunit vaccines contain purified pieces of the spike protein or other viral components.
- When administered, these vaccines stimulate the immune system to recognise the spike protein as foreign and produce antibodies against it.
- While protein subunit vaccines do not contain genetic material, they still induce a robust immune response that provides protection against infection upon exposure to the virus.
Inactivated or Killed Virus Vaccines (e.g., Sinovac, Bharat Biotech’s Covaxin)
- Inactivated vaccines contain whole viruses that have been killed or inactivated, so they cannot cause disease.
- Despite being inactive, these viruses can still stimulate the immune system to produce an immune response.
- Upon vaccination, the immune system recognises the inactivated virus as foreign and generates antibodies and memory cells.
- If exposed to the live virus in the future, the immune system is primed to mount a rapid and effective response, preventing illness.
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Prelims practise questions
Q1. What are immunomodulatory therapies used for in the treatment of vaccine-induced TTS?
(a) To increase platelet counts
(b) To suppress abnormal immune responses
(c) To activate T cells
(d) To produce antibodies
Answer: B
Q2. What do protein subunit vaccines contain?
(a) Genetic material
(b) Purified pieces of the spike protein
(c) Inactivated viruses
(d) Live viruses
Answer: B
Mains practise question
Q1. Compare and contrast the mechanisms of action of different types of vaccines available.
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