Category Archives: vaccines

more on vaccines

nice image showing the storage requirements of the two vaccines soon to be available in Australia – filched from the ABC

While I’m on vaccines, the Oxford vaccine is another. A friend sent me a link to an article in The Independent, a UK newspaper, headed ‘Oxford scientists preparing to design new versions of Covid vaccine in response to variants’. Variants are cropping up around the world at the moment, the UK variant (called B117) being followed by a South African and Brazilian variant. That’s unlikely to be the last of them. However the three leading lights re covid19 vaccines, Oxford/AstraZeneca, Pfizer/BioNTech and Moderna, all say they’ve got B117 covered, and presumably are confident about other variants. Of course the key is whether adjusted vaccines can be produced rapidly in sufficient quantities.

However, there are other issues. The possible proliferation of variants raises the question of whether we can successfully vaccinate our way out of this pandemic. The South African variant (501Y.V2) is particularly concerning, as some patients’ antibodies, after treatment, are not recognising it. It isn’t yet clear how significant this development is.

So while we await developments, I want to look at the Oxford/AstraZeneca vaccine (ChAdOx1) in a bit more detail. A few basic facts. It has been developed from a chimpanzee adenovirus, a type of DNA virus that causes relatively mild symptoms in chimps (we know of over 60 adenovirus types, many of which cause cold and flu-like symptoms in humans). It’s the vaccine of choice of the British government, unsurprisingly, and some 100 million doses have been ordered so far. It’s also cheaper (at $3 to $4US a dose) and easier to store than the two other major vaccines, which makes it the best option for poorer nations. AstraZeneca has promised to always sell the vaccine at cost to those nations.

The adenovirus has been altered to include genetic material from SARS-CoV2, so as to evoke an effective antibody and T-cell response to that virus – which has presumably been tested in clinical trials. The vaccine is described as up to 90% effective, depending on dosage, a lower percentage than the other two more expensive vaccines I’ve mentioned. Other vaccines, including Russia’s Sputnik-V and the Johnson & Johnson vaccine, have been developed from adenoviruses. Oxford researchers have found, unexpectedly, that giving a half-dose, followed weeks later by a full dose, improved efficacy by up to 90%, compared to 62% for two full doses. The reason for this result remains a mystery – further research required. It should be noted that vaccines with 60-70% efficacy are generally regarded as successful.

As I write, I’ve heard that Australia’s medical regulator, the Therapeutic Goods Administration (TGA) has approved the Pfizer vaccine for use here. Ten million doses will be rolled out in late February, after batch testing by the TGA. Why did they approve this version first? That will require further investigation, but I suspect that the greater flexibility of this new mRNA technology – all they need is the genetic sequence of a new SARS-CoV2 variant to create a vaccine to cover it – might have been a deciding factor.

However, it may well be that the Oxford/AstraZeneca vaccine, which should be approved soon, and which has been put on order, will be the most widely available, due to ease of storage and a cheaper price tag. Australia is able to manufacture this vaccine locally, so that supply shouldn’t be a problem.

Other issues – which authorities are not so willing to discuss given the need to protect high-risk individuals at the outset – are the vaccination of children, and how to deal with vaccine reluctance, or hesitancy, the new buzz-terms for anti-vaxxers. This leads to the issue of herd immunity, which I’ll discuss in my next post.

References

https://www.independent.co.uk/news/health/covid-oxford-vaccine-uk-variant-doses-b1790026.html

https://www.bbc.com/news/av/explainers-55044811

https://www.ft.com/content/49d4a7ff-a20c-4ac2-84f7-d9dbab1d431f

https://www.abc.net.au/news/2021-01-25/pfizer-vaccine-approved-australia-but-is-it-the-one-you-will-get/13088856

a brief look at mRNA biotech

from ScienceDirect: The mechanisms of different nucleic acid vaccines, including DNA vaccines, mRNA vaccines.

So it’s been three years since I’ve written on this blog, and I feel it’s time to revive it, and explore human optimism, innovation and all that positive stuff. I plan to revisit some of the innovations and pathways I’ve looked at before, to update my knowledge and check on progress, as well as checking out new developments to expand my range and keep my brain from atrophying.

So I’ll start with vaccination. The ongoing pandemic, that we here in Australia have largely dodged, has brought about an unprecedented response from virologists, completely upending the standard lag time between identifying the pathogen and having a vaccine, in fact more than one, produced in such numbers as to induce herd immunity and bring the situation more or less under control.

Not long after SARS-CoV2 was identified, drug and biotech companies began a billion-dollars race to create a big name for themselves. Two of them, Pfizer, in collaboration with German biotech company BioNTech, and Moderna, have gained the most publicity, not only for being front-runners, but for having based their vaccine on messenger RNA (mRNA).

A November 10 article from STAT+ and the Boston Globe has helped me understand the significance. The idea, once the genetic sequence of the virus is known, is to create a synthetic variant of mRNA which could then make proteins (antibodies) which would inactivate the virus.

This is the role of mRNA in all our cells. It’s translated into proteins by means of our ribosomes, and these proteins are then dispatched to perform an endless variety of roles throughout our body, including as antibodies to prevent infections, and enzymes to repair tissues. The potential of synthesising mRNA for specific purposes – to fight disease and build immunity, for example – was recognised decades ago, but every attempt to inject synthetic mRNA met with failure, as the body’s immune system recognised a chemical intruder and mounted a vigorous response. However, this problem was eventually overcome, at least partially (this is still experimental and developing technology), by swapping out one of the four nucleosides that make up every strand of mRNA for a modified version. The hybrid mRNA is able to act within cells without invoking a killing immune response. The referenced article tells the story of how this development took some years to be recognised within the biotech community, in spite of a number of published papers. It’s a human story of egos and squabbles over priority, unsurprisingly, but I just want to focus on current implications. When the technology became known in the USA, it was first mooted as a way to reprogram somatic cells into embryonic stem cells. But soon, researchers noted the vast possibilities of a technology that could induce protein production in the body for a whole host of purposes – perhaps only limited by the innumerable roles proteins naturally perform in the body.

The technology, however, still faces many hurdles, mostly related to immune responses. In recent times it has limited its focus to vaccines, and this meant that it was ideally placed to tackle the current covid-19 pandemic. Clearly we have to wait awhile for a final verdict on the two mRNA vaccines now being produced and administered around the world, but, generally, so far, so good. I’m sure there will be more to write about re synthesised mRNA technology in the future.

References

The article below, mentioned in my piece, provides a more comprehensive, and fascinating, behind-the-scenes view of some of the people involved in this technology.