New Delhi: Under the new vaccine partnership unveiled at the first Quad Summit Friday, the four-country grouping of India, US, Australia and Japan decided to pool resources and capabilities to roll out 1 billion doses of Covid-19 vaccines by 2022 as they make efforts to boost post-pandemic recovery.
As part of the plan, the US International Development Finance Corporation (DFC) will financially assist Hyderabad-based drug maker Biological E to produce doses of the Covid-19 vaccines developed in the US, including the Johnson & Johnson candidate.
Here is a look at the Johnson & Johnson Covid vaccine, the principle it works on and the challenges it faces.
The adenovirus vector-based Covid vaccine being developed by Johnson & Johnson is a single-dose vaccine, unlike most others such as the Pfizer and Moderna shots that need two doses.
While the Pfizer and Moderna products are mRNA (messenger ribonucleic acid) vaccines, the J&J shot is an adenovirus vector vaccine that works on a principle similar to mRNA but uses a different virus.
A big plus for the single-shot adenovirus vector-based vaccine that Johnson & Johnson has made is that it does not need ultra cold temperatures, unlike the mRNA vaccines.
Adenovirus is a virus that causes cold-like symptoms or flu affecting the respiratory tract of a patient. Adenoviruses are often used for viral vector vaccines because they can induce a robust immune response.
In the Covid-19 adenovirus vector vaccine, the spike protein of the SARS-CoV-2, a gene unique to the Covid virus, will be added to the adenovirus viral vector. This adenovirus will then be injected into a person’s arm. Once injected, it will get integrated with cells present in the human body. Inside the human cell, the viral vector with the help of the cell’s machinery will create the SARS-CoV-2 spike protein on the surface of the cell.
Once this spike protein is identified by the body, it will trigger both T cells and antibody response.
The efficacy factor
The vaccine has a 66 per cent efficacy result as compared to the two-dose of Pfizer or Moderna shots that have shown 94 per cent and 95 per cent efficacy, respectively.
The third phase of J&J trials in the US, South Africa and Brazil showed it was more than 85 per cent effective at preventing serious illness, and 66 per cent effective overall when moderate cases were included.
Janssen Pharmaceutical Companies, a subsidiary of the Johnson & Johnson group, has been involved in the manufacturing of the vaccine.
The company tied up with India’s Biological E last year for production of the vaccine in India.
In a press statement issued in August 2020, Janssen Pharma had said, “We are pleased to collaborate with Biological E. Limited on the manufacturing of our investigational SARS-CoV-2 vaccine candidate, Ad26.COV2.S. This agreement for the technology transfer of our COVID-19 vaccine candidate to Biological E. further expands our capabilities to deliver on our goal to make our vaccine available to citizens around the world, provided it is proven to be safe and effective.”
In October, Bio E gained approval for its phase 1/2 trials. Quoting the DGC, a report in Economic Times said: “The firm presented its revised protocol to conduct phase1\2 clinical trials of the SARS-CoV-2 vaccine along with non-clinical toxicity data before the committee. After detailed deliberations, the committee recommended grant of permission to conduct the clinical trials.”
What has now become a major discussion in the scientific community is the question of potency of the vaccine. Experts suggest once a person has been infected by the adenovirus in their natural environment, the living being develops a natural immunity towards it, rendering the vaccine ineffective.
According to the US-based Centers for Disease Control and Prevention (CDC), “Since adenoviral vectors are based on natural viruses that some of us might already have been exposed to, the vaccines might not work for everyone. To overcome this challenge, scientists have used uncommon viruses or viruses only found in other species (such as chimpanzees) as viral vectors.”
Speaking to ThePrint, Dr Satyajit Rath, visiting faculty at the Indian Institute of Science Education and Research (IISER) in Pune, explained: “The scientific community has been discussing the adenovirus and vaccine carriers for 25 years now. Logically, if a person has existing antibodies against the particular adenovirus being injected, the vaccine adenovirus when injected will not go into the body’s cells and therefore not be able to create sufficient amounts of spike protein to cause an immune response, that’s the concern.”
He added: “That is why scientists are trying to find an adenovirus that is not very common so that the vaccine is effective for all people. This is why the AstraZeneca vaccine has used a chimpanzee adenovirus, it is close enough to infect humans but has not infected humans yet.”
Another discussion, Rath said, is that the pre-existing antibodies could dampen the vaccine itself “is not necessarily proven by data”.
“There are studies that indicate that adenovirus carrying vaccines have worked on people with pre-existing antibodies but there are other studies that indicate that it doesn’t seem to make that much of a difference. The problem with this is that we don’t know yet how much of pre-existing antibodies will create this problem.”
He added: “We should keep in mind that we are injecting millions of virus particles into a spot in the human body. It means that the virus will bind itself and these barriers regarding pre-existing antibodies may be overcome with the provision of a second shot or changed potency of the vaccine.”
A study conducted by Indian scientists, published on 3 December 2020, in US-based PubMed, said: “As far as adenoviral vector vaccines are concerned, such vaccines have disappointed in past and one reason for failure as been preexisting immunity to adenovirus that hampers the immune response.”
According to another study published in Molecular Therapy, a scientific journal, the adverse effects of the adenovirus vaccines can be worrying. “In addition to swelling and pain at the injection site, common to some vaccines, Ad-based vaccine adverse effects include fever, pneumonia, diarrhea, transient neutropenia and lymphopenia, fatigue, labored breathing, headaches, liver damage, and fasting hyperglycaemia. Rare but grave adverse reactions include neuropathies such as Bell’s palsy, Guillain-Barré syndrome, gait disturbance, and transverse myelitis, an inflammatory condition in the spinal cord,” it read.
The study added: “Follow-up studies from HIV and Ebola Ad-based vaccines suggest that a 4-dose vaccine regimen can induce immune hallmarks of protection for up to 2 years. But the idea of 4 doses/person for billions of people during the first round of vaccinations—perhaps followed by booster shots every year—is difficult to imagine. So multiple shots always mean a more complicated vaccine programme. We don’t yet know how long immunity from 2 shots last for the current adenovirus vaccines.”
(Edited by Sanghamitra Mazumdar)