The Anonymous Widower

Coronavirus: Why Combining The Oxford Vaccine With Russia’s Sputnik V Vaccine Could Make It More Effective

The title of this post is the same as that of this article on The Conversation.

The Oxford–AstraZeneca COVID-19 Vaccine

This paragraph from the Wikipedia entry for the Oxford–AstraZeneca COVID-19 vaccine, gives the basic details of the vaccine.

The Oxford–AstraZeneca COVID-19 vaccine (codenamed AZD1222) is a COVID-19 vaccine developed by Oxford University and AstraZeneca given by intramuscular injection, using as a vector the modified chimpanzee adenovirus ChAdOx1. One dosing regimen showed 90% efficiency when a half-dose was followed by a full-dose after at least one month, based on mixed trials with no participants over 55 years old. Another dosing regimen showed 62% efficiency when given as two full doses separated by at least one month.

It puzzles me and I suspect it puzzles experts, that the two different vaccination regimes gave different answers.

The article on the Conversation says this.

This was intriguing. Why would giving people less of the vaccine lead to a more effective immune response? The answer to this may lie in the design of the vaccine, and could mean that there are ways to make this vaccine – and others that use the same design – more effective.

I will attempt to answer this question, in the rest of this post.

The Russian Sputnik V Vaccine

This paragraph from the Wikipedia entry for the Oxford–Russian Sputnik V vaccine, gives the basic details of the vaccine.

Gam-COVID-Vac, trade-named Sputnik V, is a COVID-19 vaccine developed by the Gamaleya Research Institute of Epidemiology and Microbiology, and registered on 11 August 2020 by the Russian Ministry of Health.

In most countries following guidelines of the World Health Organization, vaccine candidates are not approved for regular use until safety and efficacy data from Phase III trials are assessed and confirmed internationally by regulators. Gam-COVID-Vac was initially approved for distribution in Russia on the preliminary results of Phase I-II studies eventually published on 4 September 2020.

The quick approval of Gam-COVID-Vac was met with criticism in mass media and precipitated discussions in the scientific community whether this decision was justified in the absence of robust scientific research confirming the safety and efficacy of the vaccine.

In December 2020, interim analysis from 22,714 participants in a Phase III trial were published, claiming 91% efficacy with no unusual side effects.

Wikipedia says, that a medical citation is needed for the Phase III trial.

Both Vaccines Are Viral-Vector Vaccines

The Oxford vaccine is based around a modified chimpanzee adenovirus ChAdOx1, whilst the Russian vaccine is based on two human adenoviruses.

Adenoviruses are a family of viruses, that include the common cold.

The two shots of the Oxford vaccine are identical in composition, but the two shots of the Russian vaccine use a different adenovirus.

Both vaccines are what is known as viral vector vaccines.

Both vaccines would appear to deliver the same details of the spike protein of the virus to prime the body’s immune system to fight the real virus.

A Possible Problem With Viral-Vector Vaccines

This is a paragraph from the article on the Conversation, which talks of a problem with viral-vector vaccines.

When a person is given a viral-vector vaccine, as well as generating an immune response against the coronavirus’s spike protein, the immune system will also mount a response against the viral vector itself. This immune response may then destroy some of the booster dose when it is subsequently delivered, before it can have an effect. This has long been recognised as a problem.

It looks like a case of shoot the messenger to me.

The Russian Solution To The Problem

The Russian vaccine appears to get round the problem, by using two different adenoviruses in their two shots. There are fifty adenoviruses that affect humans, so they have a wide choice.

The first shot would only prime the immune system to the spike protein and one adenovirus, which could mean that the second and different adenovirus gets through without being attacked.

Co-Operation Between AstraZeneca And The Russians

This is the last sentence from the article on the Conversation.

This has now led to AstraZeneca testing a new hybrid vaccine schedule, comprising one dose of its vaccine and one of the Ad26-vector Sputnik V, to see if this makes the Oxford/AstraZeneca vaccine more effective.

I like the thinking behind this idea.

The priming for the immune system gets delivered by two totally unrelated delivery systems.

Conclusion

I wouldn’t be surprised to see this type of hybrid vaccine developed.

Surely, if we need to vaccinate every year against an ongoing Covid-19 threat, eventually, a succession of viral-vectors can be developed to fool the immune system.

The negotiation with the Russians could be tricky.

January 23, 2021 - Posted by AnonW | Health | COVID-19, COVID-19 Vaccine, Oxford University, Russia