As of 24 January 2021, over 16 lakh healthcare workers in India have received a vaccination as part of the national COVID-19 vaccination drive. The vaccination campaign isn’t yet open to the general population. But as more people are invited to get vaccinated against SARS-CoV-2, there are many questions being asked about vaccination, and the usefulness of Bharat Biotech’s Covaxin and Serum Institute of India’s Covishield – the vaccines approved for emergency-use in India – in preventing COVID-19 disease in those who have been immunised.

At the individual level, vaccines are engineered to defend the immunised person against COVID-19 disease. At the population level, vaccines lower the number of new cases of COVID-19 disease in the population. These objectives can be attained so long as the vaccines work, which isn’t a guarantee, even for tried-and-tested vaccines.

Vaccines don’t always work

For the same reason we don’t have mass vaccinations against every known infection, vaccines aren’t a sure shot protection from disease. COVID-19 vaccines are no different, experts say, and it won’t offer the same benefits to everyone.

“It’s a complex question, because it depends on what you expect of a vaccine,” said Dr Shahid Jameel, CEO of the Wellcome Trust/DBT India Alliance and Director of the Trivedi School of Biosciences at Ashoka University. “The COVID-19 vaccines are tested to answer this: Do they prevent disease?

Dr Jameel stresses the difference between COVID-19 disease and infection in the context of the vaccine. The COVID-19 vaccines, which are engineered to prevent severe symptoms of COVID-19 disease, will not prevent infection with the same efficiency.

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“When a vaccine comes out and the vaccine maker announces it is ’95 percent effective’ or ’70 percent effective’: that’s the percent of people it prevents ‘disease’ in. If it prevents disease in 70 people out of 100, 30 people may still get the disease,” Jameel adds. “The thing to understand is: many of the 30 percent will have far milder disease.”

However, the advantages and shortcomings of COVID-19 immunization with the approved vaccines are not yet fully understood. It could take anywhere from a few months to a few years to learn. “It is too early to say that these vaccines, at their stage and in this form, will be enough for everybody,” said Dr Om Srivastava, director of infectious diseases at Jaslok Hospital, Mumbai.

“They will need to be refined based on the results and outcomes from the Phase 3 trials and observations from the vaccination drive. That’s something we’ll know more about six months to a year from now.”

There are still many uncertainties about the COVID-19 vaccines, the fact that vaccines don’t always work as intended, applies to vaccines in general, and isn’t a limitation specific to COVID-19 vaccines.





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