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Covid-19 vaccine development sees unparalleled progress

US President Donald Trump's re-election campaign took off with him telling potential voters that a coronavirus vaccine will be ready by the end of 2020, even as European leaders pledged to raise US $8.3 billion to "kickstart an unprecedented global co-operation" between scientists, industry, g

overnments and philanthropies for vaccine development.

Global efforts to develop a vaccine against the coronavirus disease (Covid-19) have progressed at an unprecedented pace aiming to stop the spread of the pandemic, which has infected 3.5 million people, killed 250,000 and wrecked global economies within four months.

At least 120 vaccine projects are in various stages of development since China shared the genetic sequence of Sars-CoV-2, which causes Covid-19, with the World Health Organization (WHO) on January, 12, 2020. Of these, seven have entered human trials to test the safety and efficacy of the vaccine on healthy volunteers, according to WHO. Another 82 are in pre-clinical animal trial phases, and at least two have been found to protect monkeys from infection.

Johnson & Johnson, which was singled out by Trump as an example of vaccine success, said last month that it will be ready to produce 600 million to 900 million doses of its potential vaccine by April 2021 if human trials set to begin in September go as planned. Pfizer and the German company, BioNTech, said if their human trials are successful, they can produce millions of doses by the end of 2020.

Vaccine development, on average, takes 10.71 years from the preclinical phase, and has a market entry probability of 6%, according to a study in peer reviewed journal, PLOS One. The development includes at least three human trials to test their safety, dosage and the strength and duration of the protection they offer, followed by production, licensure, deployment of vaccines and plans for post-marketing surveillance.

"With Covid-19, the goal is to develop, test and manufacture a vaccine on a scale of hundreds of millions of doses within 12 to 18 months. Since the vaccine will be needed very quickly, an unprecedented approach has been taken by the companies. Since approvals are expected for an emergency use of the vaccine, they will start mass manufacturing as soon as they finish phase 2 trials and move to phase 3, and, in doing so, risk the failure of phase 3. In such cases, consortiums and countries fund for risk reduction and provide market commitments," said Dr N K Ganguly, former director general, Indian Council of Medical Research (ICMR).

Pune-based Serum Institute of India started work 10 days ago on manufacturing in parallel to the human safety trials, the Oxford experimental vaccine, ChAdOx1 nCoV-19, at its own risk. "SII plans to begin manufacturing the ChAdOx1 vaccine in anticipation of the clinical trials in the UK succeeding by September/October. SII will initiate the manufacture at its own risk to jump-start manufacturing and have enough doses available, if the clinical trials work," said SII CEO, Adar Poonawalla in a statement.

WHO last week organised a meeting of vaccine manufacturers and national regulatory authorities in its South-East Asia Region, of which India, Indonesia and Thailand are a part. The three countries are among the world's largest vaccine manufacturers.

"The manufacturing capacity that exists in the region is of the quality and scale required to produce and roll out a Covid-19 vaccine globally. This region is a vaccine manufacturing powerhouse, and it must now also play a lead role in overcoming the ongoing pandemic," said Dr Poonam Khetrapal Singh, regional director, WHO South-East Asia. At the virtual meeting, leading manufacturers from India, Indonesia and Thailand discussed timelines and production capacity, while regulatory bodies discussed how to fast-track processes to make large scale production and deployment of Covid-19 vaccines possible by the end of the year.

"The way this pandemic is progressing, we are left with no choice but to have an emergency use vaccine within eight months, we can't afford to wait for years. In the case of Covid-19, we already have some experience from SARS CoV-1 and MERS platforms, which have been used previously for delivering other vaccines. The same is the case with proven adjuvants [a substance which increases the body's immune response to an antigen], which could be used. So considering the fact that we are not starting from scratch, it is in the realm of possibility," said Dr Ganguly.

Last month, WHO launched the Access to COVID-19 Tools Accelerator, which brings together key global health actors, private sector partners and other stakeholders to accelerate the development and production of Covid-19 essential health technologies, including vaccines, and to help guarantee equitable access.

Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, recently said it's "within the realm of possibility" to have a vaccine widely available by January, but only if drug companies are willing to assume the risk of beginning to ramp up production of the vaccine before it is fully tested and approved.

Vaccines have led to the global eradication of small pox, and wiped out polio from most countries of the world, except Pakistan, Afghanistan and Nigeria, where it remains endemic. Vaccines for diseases such as HIV, however, remain elusive after two decades of effort.

"All countries are now preparing to safely transition towards a new normal in which social and economic life can function amid low or no Covid-19 transmission. No country is safe until we all are safe, for which an effective vaccine that is accessible to all is needed," said Dr Khetrapal Singh.

Coronavirus vaccines: types and methods

Covid-19 vaccines use a wide variety of platforms and techniques to train the immune system to identify the Sars-CoV-2 virus and block or destroy it before it infects the body.

Most vaccines feed immune cells, a signature of the unique spike protein on the surface of the Sars-CoV-2 virus, which it uses to enter human cells to cause infection.

An effective vaccine is one that generates neutralising antibodies, which store the genetic blueprint of the virus to give long-lasting protection.

At least eight vaccine types that rely on different viruses or viral parts are being developed.

Virus vaccines

At least seven teams are developing vaccines using the Sars-CoV-2 virus in a weakened or inactivated form, such as those against measles and polio. Sinovac Biotech in Beijing is testing an inactivated form of Sars-CoV-2 in humans.

Weakened virus: A virus is conventionally weakened for a vaccine by being passed through animal or human cells until it picks up mutations that make it less able to cause disease. Codagenix in New York is working with Pune-based Serum Institute of India to weaken SARS-CoV-2 by altering its genetic code so that viral proteins are produced less efficiently.

Inactivated virus: The virus is made uninfectious using chemicals, such as formaldehyde, or heat.

Nucleic-acid vaccines

Around 20 projects are using coronavirus genetic material (DNA or RNA) to prompt an immune response. The nucleic acid is inserted into human cells, which then churn out copies of the virus protein. Most coronavirus vaccines encode the virus's spike protein.

RNA- and DNA-based vaccines are safe and easy to develop: to produce them involves making genetic material only, not the virus. But they are unproven: no licensed vaccines use this technology

Viral-vector vaccines

A weakened virus, such as measles or adenovirus, is genetically engineered to produce coronavirus proteins in the body without causing disease. There are two types of weakened viruses, those that can still replicate within cells, and those that cannot, because key genes have been disabled.

Replicating viral vector (such as weakened measles): The newly-approved Ebola vaccine is an example of a viral-vector vaccine that replicates within cells to provoke a strong immune response. The vaccine is safe but existing immunity to the vector could blunt the vaccine's effectiveness.

Non-replicating viral vector (such as adenovirus): No licensed vaccines use this method, but they have a long history in gene therapy. Booster shots can be needed to induce long-lasting immunity. US-based pharma major, Johnson & Johnson, and Oxford University are using this approach.

Protein-based vaccines

Coronavirus proteins, of fragments of proteins or protein shells, that mimic the coronavirus's outer coat, are injected directly into the body.

Protein subunits: Twenty-eight teams are working on vaccines with viral protein subunits, with most of them focusing on the virus's spike protein or a key part of it called the receptor binding domain. Similar vaccines against the Sars virus protected monkeys against infection, but they haven't been tested in people. To work, these vaccines might require adjuvants, or immune-stimulating molecules delivered alongside the vaccine, as well as multiple doses.

Virus-like particles: Empty virus shells mimic the coronavirus structure, but aren't infectious because they lack genetic material. Five teams are working on 'virus-like particle' vaccines, which can trigger a strong immune response, but can be difficult to manufacture.

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