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This coming week, Oxford scientists are beginning the long road towards finding out whether their vaccine will protect humans against the Covid-19 virus. Of course, as already mentioned, there are multiple other on-going projects throughout the world, but the Oxford scientists are among the first to begin testing in humans. Sharing with you what is happening with this candidate vaccine provides a convenient example for discussing what must be done before a vaccine can be approved for widespread use. To begin with, if I was a volunteer, I’d probably like to know what I am going to be given. The vaccine consists of the spike from the Covid-19 virus (see above). This is called the vaccine antigen. Remember this term as it will be used quite a bit. Not to complicate matters too much for now, the vaccine antigen (spike) is packaged into a very small particle derived from an adenovirus, that causes the common cold. It has been modified so that it cannot cause an infection, but it can induce immunity. This adenovirus was originally isolated from a chimpanzee. (OK, I can hear the sniggers; monkey business!). It turns out to be very efficient at inducing an immune response to whatever is packaged inside it. Like all decisions, choosing this method for delivering the vaccine antigen has advantages and disadvantages. One advantage is that the Oxford team has prior experience using this approach when researching a vaccine against the Middle East Virus Syndrome (MERS). was an epidemic, not a pandemic, caused by a different Coronavirus from Covid-19. In early human testing, the Oxford MERS vaccine induced encouraging immune responses in humans, but critically, no definite proof of protection. So, starting tomorrow (April 23, 2020), human testing with the Oxford Covid-19 vaccine will commence. The Oxford Vaccine Group have recruited 510 volunteers aged 18 to 55. About half will get the Covid-19 vaccine and will be observed for six months. A vaccine against meningococcal disease (more about this and why later) will be given to the remaining 50% of participants. The main aim is to find out whether those immunised with Covid-19 vaccine are protected when compared to the comparison (control) group given the meningococcal vaccine. Of course, safety and many other detailed observations will also be carried out. But the critical outcome is whether there is evidence of protection. This raises a major point. If this stage of the testing is going to answer the key question of protection, exposure to natural Covid-19 virus must occur. If the incidence of infection in the UK falls too dramatically in the next weeks, as many might hope, then there may not be a chance to demonstrate whether (or not) the vaccine works. In other words, it’s a race against time. There is no prospect of moving forward to the next stage if the vaccine can’t be shown to protect. So, from the point of view of vaccine development what happens with rates of infection in the UK is very much a two-edged sword!Copyright Richard Moxon 22.04.2020 ................
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