In an exclusive Interview with The Daily Guardian, Dr Shahid Jameel, Virologist and Director of Trivedi School of Biosciences at Ashoka University, talks about how to judge the efficacy of a Covid-19 vaccine, how India needs to plan for the vaccination drive and whether the novel coronavirus is likely to mutate in the near future. Excerpts:
Q. What would you say about the companies claiming the efficacy of their vaccines only through press releases?
A. Press releases are quick ways for companies to make their achievements public, but they are geared more towards shareholders and financial markets. A factual position can only be judged when the scientific details of a trial are published in a peer-reviewed publication. We should wait for those. At this time, the percentage of efficacy is not important and should not be used to compare different vaccines. All this means is that vaccines based on the viral spike protein will work to protect against disease, and sometimes against infection as well.
Q. What kind of a vaccine should be given to the people?
A. A vaccine that has been proven to be safe and has good efficacy. This is the reason why human clinical trials are done in stages – Phase 1 for safety in small numbers of volunteers; Phase 2 for safety and immunogenicity in larger numbers of volunteers; and Phase 3 for safety and efficacy in very large numbers of volunteers with gender, racial and age diversity.
Q. How much efficacy should that vaccine have before being approved for people?
A. It depends upon how infectious a virus is. In this case, the WHO and US FDA have set a benchmark of 70% efficacy before a vaccine candidate will be considered for approval.
Q. Why have there been errors with the AstraZeneca vaccine?
A. I cannot answer that. All I know is what the company has said. Errors happen, but what is important is how transparently they are addressed. I am sure the regulators in all countries that want to license this vaccine will look at the data very carefully.
Q. How does India need to plan ahead for successful vaccination?
A. India’s plan should include the following. Firstly, who should get the vaccine first? The primary aim should be to use the vaccine to protect frontline workers (healthcare, sanitation, essential services), reduce mortality (elderly and those with comorbidities) and control the pandemic.
Secondly, to work out the storage-transfer-delivery logistics down to the last detail. India has a lot of experience with the polio vaccine but that was an oral vaccine not an injectable one. India also has a lot of experience with childhood and maternal vaccines, but we have never delivered such large amounts of a vaccine during a pandemic.
Thirdly, the current capacity is to deliver 1.5 million doses per month, or 18 million doses per year. The Health Minister stated that 250 million Indians would be vaccinated in 2021. That means 500 million doses. At current staff strength, it would take more than two years. Therefore, we must increase trained staff.
Fourthly, should we vaccinate those in high priority groups (e.g. healthcare workers) who have already been infected? This would make little sense and waste precious doses. If we decide not to, then there should be an inexpensive test to find out those who already have antibodies. Today the test costs as much as one vaccine dose. That cost has to be factored in.
Lastly, make the plan available for public scrutiny and comment. This will increase trust in the vaccination programme.
Q. What are the parameters which need to be considered for emergency approval of vaccines?
A. Emergency Use Approval looks primarily at safety in large and diverse populations and also a reasonable level of efficacy.
Q. For how long will these vaccines work?
A. We don’t know the answer to this simply because vaccine trial follow-ups have not been done for long enough. Extrapolating from natural infection, neutralising antibodies wane off in about six months, but that does not mean loss of protection since there are T cells and memory recall responses. Even natural infection has not been followed long enough after recovery to fully answer this question. But, going by other endemic coronaviruses, protection may last up to a year or more.
Q. Do you think this virus can mutate? If it does, what is likely to happen?
A. Every virus mutates and so does this one. RNA viruses mutate faster than DNA viruses. However, compared to other RNA viruses, coronaviruses have the lowest rate of mutation. With over 224,000 SARS-CoV2 genomes sequenced by now, mutations in the spike protein neutralizing domain have not been seen. So, that’s good from the vaccine perspective. But this region has no selection pressure on it to change. Once vaccines are deployed in a big way, such mutations will arise. We would have to watch out for that.
