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Covid 19 vaccine effects UPSC NOTE

 Covishield and TTS

  • A rare life-threatening post-vaccination complication named ‘thrombosis with thrombocytopenia syndrome’ (TTS), was the topic of well-circulated disinformation on social media.

  • The trigger for this was a court submission by Astra Zeneca that its COVID vaccine, ChAdOx1-nCoV19, manufactured as Covishield by Serum Institute in India, can in rare cases cause clots due to TTS

  • Many people mistakenly saw this as new information that to their mind explained the recent increase in heart attacks and strokes, among the youth, when this is old information about a rare side-effect that occurs in just a few people out of every million recipients

  • As far back as March 2021, after tens of millions of doses had been administered, countries in Europe and UK reported cases of TTS, a week to a month after receiving ChAdOx1-nCoV-19, with remarkably extensive thrombosis.

Risk vs Benefit

  • First, risk. TTS was found to occur most commonly in fit, healthy, young women around thirty years of age at a very low frequency of around one to two per lakh 

  • At a general population level, it was estimated to occur at only about two to three cases per million people vaccinated.

  • To put these numbers in perspective, the Ministry of Road Transport and Highways estimates annual deaths in road accidents at about ten per lakh. 

  • Thus, the highest estimated risk of TTS is still much lower than the annual risk of dying in a road accident. 

  • While we should strive to improve on both numbers, since every death that can be avoided matters, there is absolutely no reason for fear; not then, not now a couple of years after.

  • Second, benefit. Covishield was associated with over 80% protection against severe COVID-19 and over 90% protection against death in multiple studies, including during the severe Delta wave

  • For a 50% chance of contracting COVID-19 and 0.1% risk of death, this corresponds to a mortality benefit of around 40 in 100,000 - that outweighs the risk by far. 

  • The true benefit is much more than this, however. 

  • Reducing disease severity is important for minimising immediate suffering and stress on healthcare systems, as well as minimising long-term disability and risk of premature heart attacks and strokes

  • While we do not have sufficient Indian data for Covishield, it is clear from global data that COVID-19 increased the risk of subsequent thrombotic events, including heart attacks and strokes by three-four fold, even after the infection was fully resolved. 

  • This risk was observed very early in the pandemic, even before vaccines were developed, and was found to be reduced by vaccination

  • The current disinformation about vaccines and young heart attacks ignores this important data from large studies.

Importance of vaccines

  • European nations, UK, USA, and Australia stopped the use of ChAdOx1-nCoV19 / Covishield after TTS reports, despite benefits outweighing risks. 

  • They had sufficient doses of mRNA vaccines that were more immunogenic and not associated with TTS although cases of non-fatal myocarditis had been observed. 

  • Given this alternative, it was a sensible decision. 

  • For India, given the extremely large number of doses required and slow production of Covaxin, which requires culture and inactivation of the virus, it made more sense to continue

  • It seems that this is a rare side effect of the current recombinant DNA platform technology, since a similar vaccine used in America, developed by Johnson and Johnson, also increased TTS risk. 

  • Antibodies to platelet activating factor (PF4) are seen in most patients, similar to another drug-induced TTS – heparin-induced thrombosis and thrombocytopenia. 

  • Overall, it seems that the same powerful induction of immune response that makes DNA vaccines effective also carries a small risk of inducing auto-immune responses that lead to side effects. 

  • People who benefit the most from vaccines – older people and those with diabetes – seem to also be least likely to develop such aberrant responses. 

  • A similar pattern has been seen with mRNA vaccines and autoimmune myocarditis, where young healthy males were most at risk. 

  • Killed virus vaccines appear to be safer but induce lower levels of immune response, conferring lower levels of protection against severe disease and death. 

  • This was importantly seen in elderly deaths during the 2022 Omicron wave in Hong Kong.



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Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Covid 19 vaccine effects UPSC NOTE
Covid 19 vaccine effects UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
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