Known Unknowns

In conversations with family and friends these days, I am most frequently asked about COVID-19 vacci­nes. My inability to give definitive answers has ­disappointed many who get their Covid information from social media and forwarded messages. The WHO lists over 200 candidate vaccines for Covid being pursued ­seriously, including 49 being clinically tested on human ­volunteers and 11 that have moved to Phase 3 trials to test their efficacy after being shown to be safe. Considering that it takes 10-20 years to produce a successful vaccine, this speed is phenomenal, and made possible by science, new ways of testing and financing vaccines. But bottlenecks remain.

India supplies about 40 per cent of the world’s vaccines—about 2.3 billion doses, of which 74 per cent are exported and 26 per cent consumed domestically. To achieve 60 per cent coverage for 1.38 billion people—often cited as the herd immunity threshold—India would have to vaccinate 828 million people. Since all leading vaccine candidates would be needed in at least two doses, we will require 1.65 billion doses. The Serum Institute has said it can produce 300 million doses for India by the end of 2021. If Bharat Biotech and Zydus Cadila, the other Indian companies with lead candidates, add another 100 million doses, it would still take more than four years to achieve 60 per cent ­coverage. India has trained staff to deliver about 15 million doses of ­childhood vaccines each month. Though we have never ­delivered adult vaccines at this scale, at current staff levels it would take nine years to achieve 60 per cent ­coverage. Assuming each dose costs $3 (Rs 225), the minimum cost of the vaccine alone would be Rs 37,000 crore. This is over half of India’s 2020-21 central healthcare budget.

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We don’t even know which vaccines will be effective and to what extent. With Phase 3 trials either ongoing or about to start for the lead candidates in India, the efficacy won’t be fully known till the first quarter of 2021. For a vaccine that is only 75 per cent efficacious, it would take 2.2 billion doses to fully immunise 60 per cent of the population.

Some countries have considered emergency use authorisation (EUA) for Covid vaccines. India’s health minister has clarified that adequate safety and efficacy data is required for EUA vaccine approval, and that further course of action depends on the data generated. The Drug Controller General of India (DCGI), the approving authority, denied EUA to Russia’s Sputnik V vaccine based on safety data produced on small numbers of volunteers in Russia.

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The US Federal Drug Administration (FDA) and the European Medicines Agency (EMA) have clear guidelines on EUA for pandemic vaccines. “Recognising the gravity of the current public health emergency and the importance of making a vaccine available as soon as possible, we believe that a median two-month follow-up after completion of the vaccine regimen will provide the necessary safety and ­effectiveness data to support distribution of an ­investigational vaccine under an EUA,” write Philip Krause and Marion Gruber from FDA in the New England Journal of Medicine (October 16). The EMA proposes a follow-up of 70 days for pandemic vaccines instead of the usual 210 days. Emergency approval in India is further complicated by the DCGI’s inability to inspect all trial and manufacturing sites and ensuring cold chain delivery.

So, now, some of the questions I hear most often.

When would a vaccine be available? Based on available ­information, the first vaccines may be available in India by the first or second quarter of 2021.

When can I get it? If you are not a first responder, above 65 and have no major co-morbidities, you will have to wait for at least a year or two.

Which is the best vaccine? No candidate vaccine has ­completed Phase 3 efficacy trials, and all vaccines are being tested against a placebo, not evaluated against each other.

Will the vaccine protect from infection? Most vaccines in use protect against disease, not against infection. This will be no different.

How long would it protect? Even studies on natural ­infection, let alone vaccines, have not been done long enough to answer this.

The physicist Richard Feynman said, “I can live with doubt and uncertainty and not knowing. I think it is much more interesting to live not knowing than to have answers that might be wrong.” I can live with that.

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(The writer is director, Trivedi School of Biosciences, Ashoka University. Views are personal.)