Experts have said that two factors should be considered when choosing a Covid vaccine. These factors include disease enhancement (the vaccine should not behave like re-infection) and at least 3 months data on adverse events of special interest (multiple sclerosis, autism, transverse myelitis, Guillian Barre syndrome).
The doctors have pointed out that the common adverse events of a vaccine are fever, muscle pain etc.
Issuing consensus statement of doctors after a recent virtual roundtable conference on Covid vaccines’ development, Heart Care Foundation of India (HCFI) said that few vaccines may be available for distribution by the end of this year. It will be a challenge to decide which vaccine to choose.
The conference included the participation of Dr KK Aggarwal, Head-HCFI; Dr Narottam Puri, ENT specialist, Vice Chancellor of Guru Gobind Singh Indraprastha University, Prof Mahesh Varma and other senior doctors.
The doctors said that there are two types of vaccines: Protein based and non-protein based. Most vaccines use a protein component of the virus, which is immunogenic and does not require stringent cold chains.
The non-protein vaccines use the nucleic acid of the virus and require a cold chain.
The doctors noted that the Serum Institute of India is collaborating with the Oxford-AstraZeneca vaccine, which uses spike protein and the vector is chimp adenovirus. Two cases of transverse myelitis have been reported (not in India) with this vaccine in phase 3 trials.
According to doctors, the Bharat Biotech vaccine “Covaxin” is an inactivated vaccine (killed with reagent) and an adjuvant is used to increase antigenicity. Although safety will be higher, we do not know the efficacy.
They said that Sputnik V vaccine is under phase 3 trial by Dr Reddy’s Lab. This vaccine has received emergency use authorization in Russia. It contains two vectors including Adenovirus 5 and Adenovirus 26. The phase two trial in Russia was successful.
The Zydus Cadila vaccine is a DNA-based vaccine delivered by a ‘skin patch’. Phase 2 trials have been completed. It is India’s answer to Moderna and Pfizer vaccines. It is easily manufactured and can change the genetic mutations like the flu vaccine.
Moderna and Pfizer-BioNTech vaccines are nucleic acid based vaccines with >90% efficacy. These are synthetic vaccines so chances of side effects are less. Pfizer has asked for EUA in the US. If it is approved, it will be the first vaccine to be approved with full-fledged phase 3 trial.
The doctors said that the Johnson and Johnson vaccine is also a vector based vaccine. India has already started manufacture of syringes, needles, vials; cold chains are being set up. Efficacy is being affected because of cold chain. All vaccines are going to be multidose vials and their disposal will be a problem.
They have pointed out that Pfizer vaccine requires a temperature of -70 degrees C. This is a concern as we do not have this storage in the country. Storage and beneficiaries of vaccines need to be decided. How will it reach the last mile? Tier 3 and Tier 4 cities?
University of Hong Kong is working on a nasal vaccine, which may be more acceptable. It is still in the initial stage.