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NEW DELHI – “Just to be clear, this is what our vaccine (Covid-19) looks like,” said Dr. Sean Tucker, chief scientific officer of Vaxart, a U.S. biotech company, last week in a Zoom call with The Straits Times.
In his hand, there was no vial containing a solution that must be injected into the muscle, as the currently available Covid-19 vaccines are administered.
Instead, he showed a single pill in a blister pack – a tantalizing prospect that people could soon pop a Covid-19 vaccine like they would with any regular pill.
As countries try to overcome the worrying spread of the coronavirus with faster vaccination deployments, many have been constrained, not only by a limited supply of vaccines, but also by their inability to use the available doses because they lack the necessary resources. cold chain or health care infrastructure. personnel needed to administer them.
It is this unprecedented challenge in vaccine storage and delivery that San Francisco-based Vaxart hopes to solve with its Covid-19 tablet vaccine that could be used worldwide without the limitations of needle vaccines.
“You can potentially send it by mail or drone, or, you know, drop them. That’s the benefit of having a vaccine in pill form,” Dr Tucker told ST. “There is no learning involved or qualified medical support to follow it and it avoids the cold chain. This is a huge advantage.” Vaxart’s tablet vaccine candidate is currently in phase II trials.
The Covid-19 vaccines in use require some form of cold storage to remain effective, such as the one from Oxford-AstraZeneca which needs to be stored in conditions between 2 degrees C and 8 degrees C, and the one from Pfizer which requires storage. cold to minus 70 degrees C..
This has proven to be a challenge in low- and middle-income countries, where a 2018 study found that 59% of healthcare facilities lacked reliable electricity to power cold storage devices.
It is not only in parts of Africa or India that the lack of such cold storage facilities has proven to be an obstacle, but also in rural areas of the United States and the outback Australian.
The “hot vaccines” under development would be much easier to store and distribute in such locations, revolutionizing the pandemic response in hotter, resource-poor regions.
An encouraging step forward was reported last month when such a vaccine developed by the Indian Institute of Science (IISc) and biotech start-up Mynvax was shown to be able to trigger a strong immune response in mice and protect hamsters from coronavirus.
The vaccine generated antibodies capable of neutralizing four Sars-CoV-2 variants, including the highly contagious Delta variant. The researchers, including those at CSIRO, Australia’s national science agency, also reported that the vaccine remained stable at 37 ° C for a month and at 100 ° C for 90 minutes.
Dr Raghavan Varadarajan, professor at IISc and one of the two co-founders of Mynvax, told ST that the vaccine will most likely be available as a lyophilized powder with liquid adjuvant in a separate vial. An adjuvant is an ingredient used in vaccines to help create a stronger immune response.
Both components can be stored at room temperature and easily transported. They will need to be mixed together to create the vaccine solution for intramuscular injection. Clinical trials of the vaccine candidate are expected to begin in six months, and public deployment is not expected for at least 16 months.
Like many other countries, India has also struggled to speed up its vaccination program and administered an average of four million doses per day. Just under 10% of India’s population has been fully vaccinated and the potential need for repeated doses to maintain immunity against the coronavirus has heightened the urgency for vaccines that can be deployed quickly.
This is where hot vaccines such as that from IISc-Mynvax, which are expected to be sold for less than vaccines currently in use in India, could prove particularly useful in the campaign against Covid-19. Yet, little research has been done to produce hot vaccines around the world.
A commentary published in The Lancet in March this year noted that high-income countries were not “really interested and committed” to developing thermostable vaccines because their refrigeration capacity was never seen as a limiting factor.
That’s why, he said, heat-tolerant vaccines have never been prioritized by vaccine developers, industries and funding entities despite their demand from low- and middle-income countries.
It was this neglected demand for heat-tolerant, easy-to-administer vaccines that Dr. Tucker sought to address. Vaxart now specializes in the manufacture of tablet vaccines, particularly against noroviruses as well as against seasonal influenza.
In May, its Covid-19 vaccine candidate reported encouraging Phase I results, showing higher CD8 + T cell responses than the Pfizer and Moderna vaccines. CD8 + T lymphocytes are a type of white blood cell responsible for generating an immune response. If all goes well, Vaxart hopes to apply for emergency use authorization within a year.
The company expects to produce millions – if not billions of doses of its vaccine – each year at a price that Dr. Tucker has called “profitable.”
An oral vaccine could also help reduce vaccine reluctance caused by reluctance to get bitten.
The results of a poll commissioned by Vaxart earlier this year indicated that nearly 19 million more American adults – about a third of those who now refuse to get bitten – would get the shot if they could take a pill at home. place to get vaccinated.
Developing an oral vaccine formulation has been a challenge as they don’t always work in humans the same way they do in animals. The Vaxart team has been dedicated to ensuring the best results in humans, even identifying the ideal parts of the intestines for the tablet to open and maximize impact.
The vaccine deploys a two-step defense mechanism, the first of which is to trigger an antibody response from the mucous membranes that form the moist inner lining of certain organs and body cavities such as the nose, mouth, lungs and stomach. If it works, this approach could effectively kill the virus in the upper respiratory system itself, dramatically reducing the chances of an individual falling ill with Covid-19.
However, if it fails and infection sets in, the CD8 + T cell response is the back-up defense plan. “Our technology can handle and attack the virus on several fronts which are different from injected vaccines,” said Dr Tucker. “This is likely to eliminate the virus much faster.”
In the case of the IISc-Mynvax candidate, Dr Varadarajan said there was no challenge in ensuring that their vaccine remained heat tolerant, an attribute they wanted when developing the plans for the vaccine.
“If we had gotten multi-million dollar on day one, we would also have had our vaccine on the market now,” he added, noting how many policymakers at the start of the pandemic thought the coronavirus outbreak was going to be limited and ultimately controlled with a varied but limited supply of vaccines.
A major challenge for Dr Varadarajan and his colleagues came when they had to choose the right adjuvant solution to rehydrate their lyophilized vaccine powder and improve its performance. There are not many adjuvants available on the market, let alone in the public domain, and the wrong adjuvant choice could potentially lead to an unfavorable or suboptimal immune response.
“The one thing you don’t want to have in a vaccine is the increased likelihood of someone getting the disease,” he told ST. Their vaccine uses an unpatented squalene-in-water emulsion adjuvant. Developing a new adjuvant is a time consuming, difficult and risky endeavor.
While much of the funding for global research has gone into new vaccine technologies such as those using mRNA, funding in India has gone primarily to large manufacturers who have linked up with these foreign vaccine developers.
Even today, there aren’t many hot vaccines in the works. The BBC reported this week that Iconovo, a Swedish company that produces inhalers and dry powder formulations for pharmaceutical companies, is collaborating with an immunology research start-up in Stockholm, ISR, which has developed a powdered vaccine. dries against Covid-19.
It uses manufactured Covid-19 virus proteins and can withstand temperatures up to 40 ° C. The company is currently testing its vaccines on beta and alpha variants of Sars-CoV-2.
Ziccum, another Swedish company, is also testing its technology designed to air dry existing or future liquid vaccines without limiting their effectiveness. The vaccine powder should be mixed with a sterile water solution before it is injected.
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