Context

The COVID-19 pandemic has exacerbated an anti-vaccine movement, previously limited to niche communities, either skeptical about vaccine benefit, or suspicious of vaccination motives. 

Risks and Benefits Associated with COVID-19 Vaccines

• Different Approaches to COVID-19 Vaccines: In some nations, with other available highly effective options, recombinant DNA vaccines were paused.
  • In India and other nations, a risk-benefit analysis, and consideration of alternatives, favoured continuation.
• Risk of Thrombosis with COVID-19 Vaccines: Thrombosis with Thrombocytopenia Syndrome (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 (100,000).
  • At a general population level, it was estimated to occur at only about two to three cases per million people vaccinated.

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• Risk Comparison: To offer some context, the Ministry of Road Transport and Highways approximates annual fatalities from road accidents at roughly ten per lakh. Hence, even the highest projected risk of TTS remains significantly lower than the annual likelihood of perishing in a road accident.
• Covishield’s Efficacy and Mortality 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.
• Reducing Disease Severity: Reducing disease severity is important for minimizing immediate suffering and stress on healthcare systems, as well as minimizing long-term disability and risk of premature heart attacks and strokes.
  • 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.
• Vaccine Benefit: 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.

COVID-19 Vaccines Side Effects 

• Rare Side Effects of DNA Vaccines: 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.
• Commonality with Drug-Induced TTS: Antibodies to platelet activating factor (PF4) are seen in most patients, similar to another drug-induced TTS – heparin-induced thrombosis and thrombocytopenia.
• Vaccine Immune Response : 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.
• Less Effective: 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.

Way Forward

• Need for Better research: As in much of medicine, there is no perfect choice. Further research is essential to maximise benefits, minimise risks, and increase alternative options.
  • However, at any given point of time, a decision must ultimately be made within available options, given available knowledge.
• Global Covishield Experience: Despite having given nearly a billion doses of Covishield, almost all our knowledge of critical side effects like TTS comes from outside India.
• Innovating Vaccine Alternatives:While it is acceptable to choose an imperfect best option, we need to be nimbler in creating alternatives.
  • For example, protein-subunit vaccines like Covovax (also made by Serum Institute) could have replaced Covishield for boosters.
• Silent Surges: SARS-CoV-2 remains persistent, continually evolving to evade immunity, leading to occasional surges in infections. These spikes often go unnoticed due to milder symptoms in individuals with partial immunity.
  • For instance, recent analysis of viral load in sewage and wastewater sequencing revealed a concealed surge of undiagnosed JN.1 SARS-CoV-2 infections in January.

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Conclusion

To conclude, vaccines are some of the most effective public health interventions against infectious

diseases. We need to stop the fear-mongering and celebrate the great Indian COVID-19 vaccination drive that saved innumerable lives.