India has introduced 2 Covid19 vaccines in the largest vaccination drive ever done in the world. COVAXIN® is India’s indigenous COVID-19 vaccine by Bharat Biotech is developed in collaboration with the Indian Council of Medical Research (ICMR) – National Institute of Virology (NIV). The other vaccine is Covishield.
Covaxin – The indigenous, inactivated vaccine is developed and manufactured in Bharat Biotech’s BSL-3 (Bio-Safety Level 3) high containment facility.
The vaccine is developed using Whole-Virion Inactivated Vero Cell-derived platform technology. Inactivated vaccines do not replicate and are therefore unlikely to revert and cause pathological effects. They contain dead virus, incapable of infecting people but still able to instruct the immune system to mount a defensive reaction against an infection.
What is unique about an Inactivated Vaccine?
Conventionally, inactivated vaccines have been around for decades. Numerous vaccines for diseases such as Seasonal Influenza, Polio, Pertussis, Rabies, and Japanese Encephalitis use the same technology to develop inactivated vaccines with a safe track record of >300 million doses of supplies to date. It is the well-established, and time-tested platform in the world of vaccine technology.
Key characteristics of COVAXIN
- COVAXIN® is included along with immune-potentiators, also known as vaccine adjuvants, which are added to the vaccine to increase and boost its immunogenicity.
- It is a 2-dose vaccination regimen given 28 days apart.
- It is a vaccine with no sub-zero storage, no reconstitution requirement, and ready to use liquid presentation in multi-dose vials, stable at 2-8oC.
- Pre-clinical studies: Demonstrated strong immunogenicity and protective efficacy in animal challenge studies conducted in hamsters & non-human primat.
COVAXIN® Effective Against Variants of Concern
It has proven to neutralize the variants – B.1.1.7 (Alpha) first isolated in UK, P.1- B.1.1.28 (Gamma) & P.2 – B.1.1.28 (Zeta) first isolated in Brazil, B.1.617 (Kappa) first isolated in India, B.1.351 & B.1.617.2 (Beta & Delta) first isolated in RSA & India.
Efficacy data demonstrates 65.2% protection against the SARS-CoV-2, B.1.617.2 Delta variant.
COVAXIN® demonstrated 77.8% vaccine efficacy against symptomatic COVID-19 disease, through evaluation of 130 confirmed cases, with 24 observed in the vaccine group versus 106 in the placebo group. The efficacy against severe symptomatic COVID-19 disease is shown to be 93.4%. The efficacy data demonstrates 63.6% protection against asymptomatic COVID-19.
What kind of vaccine is COVISHIELD?
It is a recombinant, replication-deficient chimpanzee adenovirus vector encoding the SARS-CoV-2 Spike (S) glycoprotein. Following administration, the genetic material of the part of coronavirus is expressed which stimulates an immune response.
Covishield has been prepared using the viral vector platform which is a totally different technology.
A chimpanzee adenovirus – ChAdOx1 – has been modified to enable it to carry the COVID-19 spike protein into the cells of humans. Well, this cold virus is basically incapable of infecting the receiver but can very well teach the immune system to prepare a mechanism against such viruses.
Very rare events of serious thrombosis with thrombocytopenia, including unusual sites such as cerebral venous sinus thrombosis and splanchnic vein thrombosis, some associated with arterial thrombosis, have been observed following vaccination during post-authorization use.
The majority of the events occurred within the first 14 days following vaccination whereas the outer limit was 33 days and some events had a fatal outcome.
What does COVID19 Vaccines data suggest?
The data suggest that two doses of mRNA vaccines are needed for good protection against the Delta variant, but it is not clear how long that immunity lasts, especially among the immunosuppressed or elderly. Israel is seeing some disease in vaccinated people and has started a third dose.
However, the priority is to make more vaccines for the primary course rather than a booster, because even if vaccinated people get sick, it is less likely that they will die. Though I must say that we are moving to a situation where an updated vaccine could be used. Flu vaccines are updated every year, so we may end up in a similar situation with Covid-19. Vaccines will still be protective to an extent against severe disease and against most mutant strains at present, but we need to keep monitoring.
Which of these covid19 vaccines is the most effective. Can a mixing of vaccines work?
According to experts, most vaccines are effective against very severe diseases and death. But there remain questions on duration and breadth of immunity. Data shows that vaccines currently administered work well when mixed: one dose of each… though it may depend on which one is given first.
Covaxin data looks very promising. It is important to look at effectiveness against severe disease and not a mild disease. At the severe end of the spectrum, vaccines start to converge ineffectiveness.
