This is slated to be the year of minimising the impact of COVID-19 . While mutants of the virus pose a new threat, the only viable strategy to curb COVID-19 has been to develop vaccines. The fast-paced scientific work done to develop the vaccines is unparalleled. Within a year of COVID-19 being identified, several vaccines have become available. What do we know about these vaccines?
Types of vaccines
The result of the trial of Pfizer and BioNTech’s mRNA-based COVID-19 vaccine was submitted to the U.S. Food and Drug Administration in December 2020. It showed 95% efficacy in adults ages over 65. However, the infrastructure for the delivery and storage of the vaccine under fastidious requirements of -70°C is not easy to achieve. Equally, this vaccine has come under a cloud, with 29 deaths of elderly people with pre-existing illnesses reported in Norway following administration of 42,000 doses. Moderna using mRNA-based vaccines and Johnson & Johnson using DNA-based vaccines are also being developed in the U.S. These vaccines are unlikely to come soon to India because of cost and storage requirements.
The first heterologous COVID-19 vaccine consisting of two components has been used in Russia with good initial reports. However, this adenovirus-based vector vaccine, Sputnik V, was released after Phase 2 studies in a very small number of volunteers and the protocols were not published. Other countries to get a nod for its use are Serbia, Argentina, Bolivia, Algeria, and Palestine. It has reportedly been administered in more than a million people in several countries without safety concerns. In India, Dr Reddy’s Laboratories is using Sputnik vaccine in a placebo-controlled Phase 3 trial with 1,500 volunteers. The results are expected by mid-2021.
The chimpanzee adenoviral vector vaccine by Oxford University-AstraZeneca is the only vaccine in India which has completed Phase 3 trial. The large placebo-controlled trial of 23,848 volunteers in the U.K. and Brazil has shown an acceptable safety profile along with increased antibody response by homologous boosting. The Drugs Controller General of India gave approval for its use in India on January 2 and it is being rolled out under the name Covishield. The Serum Institute of India in collaboration with AstraZeneca has produced a stockpile of 50 million Covishield vaccines which has been sent to all the States. This vaccine can be stored and transported easily.
Then we have the adenovirus vector-based Covaxin by Bharat Biotech, which is in Phase 3 trial with a goal of 26,000 volunteers. The results are expected only after three months or so. Yet this vaccine has been rolled out in India for restricted use in clinical trial mode which lacks clarity.
The States and priority group beneficiaries don’t have the option to choose whether they receive Covaxin or Covishield . Consequently, uptake amongst health professionals has significantly reduced. As per established protocols and ethical norms, the immunogenicity and safety data from Phase 1 and 2 trials are not enough for approving the clinical use of a vaccine. Without Phase 3 trial data, confidence in the safety and effectiveness of Covaxin will remain questionable. It is noteworthy that due to inadequate immune response of two vaccines using inactivated virus, Merck & Co in the U.S. abandoned its trials.
Zydus Cadila is developing two COVID-19 vaccines. The company’s novel DNA-based vaccine will complete Phase 3 studies by mid-March before applying for approval. It is appropriate for the company to wait until Phase 3 results are available.
In addition to these, there are at least two more vaccines in various stages of development in India. Biological E is working on a protein-based vaccine in collaboration with the Baylor College of Medicine, U.S. The company is conducting Phase 1 trial. Phase 2 trial may begin in March. Gennova’s vaccine is India’s first mRNA COVID-19 vaccine that can be stored at 2°C-8°C. Phase 2 trial of this vaccine is likely in March. Outside of India, there are about 60 other vaccines undergoing clinical trials globally.
Also read | Indian scientists divided over nod for Covaxin
How do we choose a vaccine?
Our choice of the vaccine has to be dependent on whether the data have been gathered with scientific rigour. Each trial should involve an adequate number of volunteers; studies need to have a control or placebo arm; protocols of the studies should be in the public domain and in peer-reviewed scientific journals; and Phase 3 trials should be completed with an adequate number of volunteers and observation periods of adequate length with the results reviewed by experts. Trial outcomes need to be scientifically validated and should not be influenced by political pressure and deadlines. The aim must be to effectively and safely protect the population and make COVID-19 innocuous.
Also read | Vaccine dilemma — to take or not to take Covaxin
Upendra Kaul is Chairman Cardiology and Dean Academics and Research, Batra Hospital, New Delhi; and Meera Shah works in Public Health in rural India
