A vaccine against coronavirus available sooner than expected? Pharmaceutical group AstraZeneca has announced they were able to put 300 million doses of their vaccines into circulation from September 2020. They explained they are “able to produce one billion doses of the ChAdOx1 n-CoV-19 vaccine against SARS-CoV-2 responsible of Covid-19” as our peers from Sud Ouest say.
But how does this candidate vaccine work? It is live and recombinant, relying on the use of a chimpanzee’s adenovirus (a medium-sized virus which genome is made of double-strand DNA, also known as complementary RNA), genetically modified “to be used as viral vector”. This viral vector – called ChAdY25/ChAdOx1, aims at making the immune system react by producing virus proteins or other diseases and create a response.
Clinical trials have been made in this molecule in 2018 already to fight against Influenza, and in 2020 to wipe out two other diseases: tuberculosis and MERS. Experimental vaccines that delivered satisfactory results, including a specific immune response, which structure has been used to set up a molecule likely to spark an immune response against Covid-19. But nothing shows these vaccines could genuinely protect people who have been included in these clinical trials. And for good reasons: these studies only include 50 people, all being grown-ups and healthy.
This past May, as Sud Ouest daily says: “a study assessing the capacity of ChAdOx1 n-CoV-19 to spark a specific immune response and protection against SARS-CoV-2 in animals (mice and rhesus monkeys) has been published in preprint” with rather interesting results since guinea pigs who have been given the candidate vaccine in the trial produced specific antibodies and showed 28 days later “a lowered viral load in lungs” in comparison with those given a placebo.
In April 2020, first tests in humans have been performed in Great Britain in volunteers who are healthy and aged between 18 and 55. The first phase of the clinical trial is said to end by May 2021. The second phase of the trial, including over 10,000 people of all ages is currently developed. But research may go fast, it is a bit bold to put a vaccine into circulation while the first results are barely known. AstraZeneca bets their vaccine will work, therefore it will be available from September, while others will wait for more viable and more certain results. A bet that may cost a lot if it ends up ineffective as well.