The year 2020 has been a challenge for humanity. Nearly a year has passed since the beginning of Coronavirus pandemic but the hunt to find a perfect vaccine for the deadly virus is still on. Amidst this, several countries, including India, have given approval to several vaccine candidates for limited emergency use.
In India, Bharat Biotech’s Covaxin and Serun Institute of India’s Covieshield have been approved, paving the way to launch the world’s largest vaccination against COVID-19 from January 16. As India prepares to launch its vaccine drive on January 16, here is a look at the main COVID-19 vaccines candidates and where they stand now:
COVAXIN
Developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology, the indigenous vaccine has been granted emergency use authorisation in ‘clinical trial mode’ by the Indian government.
It is an “inactivated” vaccine developed by chemically treating novel Coronavirus samples to make them incapable of reproduction. This process leaves the viral proteins, including the spike protein of the Coronavirus which it uses to enter the human cells, intact.
Given as two doses, three weeks apart, the viral proteins in the vaccine activate the immune system and prepare people for future infections with the actual infectious virus. According to Bharat Biotech, the therapeutic can be stored at room temperature for at least a week.
A study on the Phase 1/2 trial published in the preprint server medRxiv in December showed the therapeutic doesn’t cause any serious side effects. However, there has been no further data released in the public domain which could demonstrate that the vaccine is safe and effective.
COVISHIELD
Co-developed by the University of Oxford and British-Swedish company AstraZeneca and known as Covishield in India, the vaccine was the first on which a scientific study was published based on Phase 3 clinical trials.
It has so far been given emergency use authorization in the UK, Argentina, Mexico and India. Scientists have engineered a version of adenoviruses that infect chimpanzees to carry the gene responsible for the spike protein of the novel coronavirus.
It requires two doses, provided four weeks apart, to produce the desired effects.
Manufactured by the Serum Institute of India, Covishield will be sold at Rs 1,000 per dose in the private market but cost the Indian government only Rs 200, said SII CEO Adar Poonawalla,
“Oxford-AstraZeneca-Serum Institute vaccine has shown protective efficacy in global trials to the tune of 60-70 per cent. While clear data from bridging trials in India are not available, the vaccine is certainly proven safe,” Bal said.
According to virologist Upasana Ray from the CSIR-Indian Institute of Chemical Biology, Kolkata, the AstraZeneca-Oxford vaccine is less restricted in terms of cold storage as it can be stored, transported and handled at normal refrigerator temperatures (2-8 degrees Celsius) for at least six months.
MODERNA
The mRNA vaccine by US-based company Moderna has so far been approved for use in Israel, the EU, Canada and the US.
A study of the efficacy of Moderna vaccine revealed it has 94.1 per cent efficacy in preventing the disease. In this type of vaccine, the messenger RNA — or mRNA — acts as a blueprint for the production of the coronavirus spike protein and is encapsulated by lipid molecules and delivered into human cells.
The cells of the vaccine recipient then use this mRNA genetic code to produce the viral protein to train the immune system for a future encounter with the infectious Coronavirus.
Administered as two doses, four weeks apart, the Moderna vaccine can reportedly be stored in the refrigerator at 2-8 degrees Celsius for up to 30 days. At -20 degrees Celsius it can be stored for up to six months. This is still a challenge for many developing countries in the tropical regions that experience very high temperatures in the summer months.
PFIZER-BIONTECH
The US-backed Pfizer-Biontech’s COVID-19 preventive, like the Moderna vaccine, is based on the segments of the genetic material of the novel Coronavirus. Preliminary data from the clinical trials showed that two doses of the vaccine, given three weeks apart, provided an efficacy of over 90 per cent.
Following the results, the UK, Canada, the EU and Saudi Arabia have approved the Pfizer vaccine for use. Several countries, including the US, Singapore, Argentina and Mexico, have given emergency use authorisation.
One limitation for the Pfizer vaccine has been its requirement for ultracold storage — up to -70 degrees Celsius.