Interim Phase 3 Results Of COVID-19 Vaccine Covaxin ‘Encouraging’, More Data Needed: AIIMS Director

New Delhi: Phase 3 results of the indigenous COVID-19 vaccine Covaxin, developed by Bharat Biotech International Limited (BBIL) in partnership with Indian Council of Medical Research (ICMR), has shown an interim vaccine efficacy of 81 per cent in preventing COVID-19, revealed Bharat Biotech on March 3. The phase 3 trial was initiated in mid-November 2020, covering a total of 25,800 individuals across 25 sites. Covaxin is one of the two COVID-19 vaccines to have got emergency use license in India. Covaxin was cleared by the Drug Controller General of India (DCGI) in early January on the basis of Phase I and II data that confirmed its safety and immunogenicity. NDTV spoke to AIIMS Director Dr Randeep Guleria, who himself has got both the doses of Covaxin, to understand the interim analysis better.

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Dr Guleria called the interim data encouraging but said the trials will continue as more data is needed for final analysis. He explained,

We already had data from phase 1 and phase 2 which showed good neutralising antibodies and there was also enough data to suggest safety but one wanted to look at the efficacy data. However, one should keep in mind that this is the interim result because they need to have 130-140 odd COVID positive cases to analyse the data. This is the interim result of 43 subjects who got COVID and they looked at how many of them were in the placebo arm (people who are not given vaccine) as compared to those in the vaccine arm.

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Covaxin’s Phase III trials, which began in November last year, involved 25,800 participants aged between 18 and 98 across 25 sites. Over 2,000 participants (2,433) were over 60-year-old and 4,533 participants had co-morbidities. The trial is being called the largest clinical trial ever conducted in India. Elaborating on the need for additional data, Dr Guleria said,

In terms of people who are enrolled in the trial, this is the largest trial conducted in the country on Indian subjects. But really to see the efficacy, you want to have a sufficient number of people who get infected with COVID-19 and then you don’t know which group has got the vaccine and which has got the placebo. When you have a sufficient number of people who have got infected which can give you a statistically significant number which is calculated before the trial was done and the sample size was calculated then you can say that yes, this is the efficacy which is based on a good number which is significant and currently the data is interim.

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Dr Guleria explained that after 43 individuals from over 25,000 participants got COVID-19, the code was broken to see who got the vaccine and who got the placebo.

In the placebo arm, there were 36 people who got the COVID-19 infection, whereas, in the vaccine arm there were only 7. Based on that, the calculation showed that the vaccine efficacy is around 81 per cent. But we will need to have around 130 people who get the infection and then we again break the code and see how many of them are in the vaccine arm and how many are in the placebo arm to get real efficacy data, but the interim result is very encouraging and I think that should be a big boost to the vaccination programme in our country.

Dr Guleria confirmed that phase 3 trials will continue as the final analysis is planned for 130 cases. An interim analysis is done to ensure you are going in the right direction and the vaccine is effective, he added.

Dr Guleria also suggested vaccine developers to put the interim data in the public domain and get it peer-reviewed. He said,

Everyone can look at it critically both in terms of what was the protection, how much did it (vaccine) protect from a severe infection, did it give some protection even from mild infection or not getting the infection at all and what was the morality benefit that it had. There are a lot of secondary endpoints which can also be looked at as far as data is concerned.

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Dr Guleria noted that another positive thing about Covaxin trials is that it covers the elderly and people with comorbidities. He said,

Many of the vaccines which were initially out excluded those with comorbidities and the elderly age group because they were not sure about the safety and they wanted to see efficacy in a group where the immune response would be robust enough. Again, this is something which is very encouraging and as we get more data out, it will also be useful to see what was the protection in those over the age of 60, in those who had comorbidities and was it the same as compared to those who are less than 60 or in the younger age group and those who do not have comorbidities.

Going forward, Dr Guleria recommends focusing on two things – firstly, eliminating vaccine hesitancy and reassuring citizens that the data is encouraging and they should get vaccinated; secondly, continue the trials to see the final efficacy which may go up as more and more people get the infection.

The interim result is very encouraging and I think it should put all sorts of doubts at rest and we should really look forward in terms of promoting this vaccine also in a big way as far as our national vaccine programme is concerned. We need to vaccinate a large number of people in our country to be able to prevent the pandemic from progressing further, said Dr Guleria.

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