Rollout of Covid-19 vaccine
Source: By Prabha Raghavan: The Indian Express
India’s top drug regulator on 3 January 2021 approved Covishield and Covaxin as vaccines for restricted use against Covid-19, paving the way for mass vaccination against the virus that has so far infected over a crore people and killed nearly 1.5 lakh.
Covishield is the Indian variant of AZD1222, the vaccine developed by AstraZeneca and University of Oxford. Pune-based Serum Institute of India (SII) developed and manufactured Covishield through a licence from AstraZeneca and Oxford.
It is a “non-replicating viral vector” vaccine, which means it makes use of another weakened and genetically modified virus — in this case a common cold chimpanzee virus — to help the body develop immunity against the coronavirus. The vaccine carries just the code to make the spike protein (the spike on the virus’s surface). The body’s immune system is supposed to recognise this protein as a threat, and work on building antibodies against it.
Covaxin, developed by Hyderabad-based Bharat Biotech in collaboration with the National Institute of Virology, uses a different platform. It is an “inactivated” vaccine, which means it uses the killed SARS-CoV-2 virus, which has no potential to infect or replicate once injected and just serves to boost an immune response. Covaxin is expected to target more than just the spike protein — it also aims to develop an immune response to the nucleocapsid protein (the shell of the virus that encloses its genetic material).
Both vaccines have received what is known as a “restricted use approval in an emergency situation” — similar to an Emergency Use Authorisation that countries like the UK and US have been granting to companies like Pfizer, Moderna and AstraZeneca for their vaccines.
This means the vaccines have been approved for use despite the companies not having completed clinical trials. Given the pandemic, the government wanted a vaccine ready to use at the earliest. Another growing concern is the mutation of the SARS-CoV-2 virus that has led to newer strains in countries like the UK which are starting to spread to other parts of the world, including India.
Covishield secured a restricted approval with the help of data generated from over 23,000 participants in AZD1222’s trials in countries like the UK and Brazil. An expert committee of the regulator found Covishield compared with AZD1222 after looking at this data as well as interim data from the vaccine’s phase 2/3 trials on 1,600 participants in India.
In the case of Covaxin, the regulator felt it needed to be approved because it felt the inactivated platform would be able to protect against mutations. The regulator looked at animal testing data as well as data on safety and immunogenicity (ability of the vaccine to prompt an immune response) from phase 1/2 trials.
Several conditions have been imposed on SII and Bharat Biotech, including that both firms have to continuously submit safety, efficacy and immunogenicity data from their ongoing trials until these are complete.
They also have to submit safety data every 15 days for the coming two months and after that monthly for the duration of their trials.
On top of this, the restricted approval to Covaxin has been given “in clinical trial mode”. Bharat Biotech will still have to complete vaccinating nearly 26,000 participants in its phase-3 trial, and then collect and analyse data from these people. Bharat Biotech was earlier testing its vaccine by giving half of its participants a placebo. According to the firm, everyone it is testing now will be given Covaxin and data on safety and efficacy will be analysed from them over a fixed time period. Bharat Biotech will have to submit a protocol for this trial, and a risk management plan.
Some scientists have expressed concern about the basis for the approval of Covaxin, given that it does not seem to adhere to the regulator’s own requirements for clearing a vaccine in this pandemic.
Health Minister Dr Harsh Vardhan has described the approval for Covaxin as a “strategic decision for our vaccine security”. This approval ensures India has an additional vaccine shield in its arsenal especially against potential mutant strains in a dynamic pandemic situation – A strategic decision for our vaccine security.
