Is the South African variant exposing weakness in Oxford-AstraZeneca vaccine?

An uneven response to Covid-19 variants has developed into a crunch issue

With Covid-19 it seems that as soon as a sustained positive trend emerges, another twist crops up elsewhere bringing new uncertainty and fear. In that regard, the emergence of more infectious new variants is the culprit of late.

Just as Europe is seeing a sustained decline in cases, a range of variants are causing alarm, of which the South African strain is causing most concern.

Emerging variants are the inevitable consequence of a virus that is continuing to spread. That is why quick rollout of vaccines across the world – and not just rich northern hemisphere countries – is so critical.

The hard reality is variants will increase in intensity in parts of the world; some will be nastier than the original version, as evidenced by research suggesting the UK strain is more deadly.


With troublesome variants, deploying measures that are known to work is essential. More and more, it is clear this should include coherent international action; not the haphazard, inconsistent approach of individual countries.

What is so problematic with the South African variant?

A study shows that when the Oxford-AstraZeneca vaccine is used, it does not protect people infected with this strain from mild to moderate Covid.

It has become widespread and can apparently dodge key antibodies. It has not taken hold in Europe, where the UK variant of the virus is increasingly dominant, but 11 cases have been detected in Ireland.

The problem is the Oxford-AstraZeneca vaccine is the mainstay of the UK government’s immunisation plans, and is vital globally because it’s cheap and easy to administer. Its makers hope it will be widely used in developing countries, insisting they can produce 3 billion doses this year; far more product at a far lower price than other vaccines.

Will the South African variant scupper use of a key vaccine in the fight against Covid-19?

Probably not. The study carried out by Oxford-AstraZeneca scientists with University of Witwatersrand researchers in South Africa was on a relatively small number of people – 2,000 with an average age of 31. This means they were relatively young and at lower risk.

So scientists cannot yet be certain protection remains against serious disease, but they think it’s likely. Those vaccinated did have the benefit of a second dose, which is proven to strengthen immunity. They are hopeful it might still prevent severe disease, hospitalisation and death.

And it should be noted, nobody in this study developed severe disease or required hospitalisation.

What about herd immunity?

The threshold for herd immunity with Covid-19 is estimated to be between 60 and 90 cent of the population; that is the proportion of people who need to have immunity either from vaccination or from prior infection.

Technically, a population reaches herd immunity when the average number of people infected by a single sick person falls below one.

Achieving herd immunity is not helped by the presence of more infectious or more virulent variants taking hold in large pockets of the world.

So in the race between vaccines and variants (South African version included), it’s critical that vaccination takes root in all parts of the world, notably that a majority of people avail of a jab as swiftly as possible.

Is there any cause for hope in the face of variants bringing renewed and heightened risk?

Inevitably new restrictions are being introduced in response to menacing variants and in a desperate effort to avoid a fourth surge. That includes more rigorous quarantining in relation to international travel.

While there is renewed doubt about timelines on a return to some form of normality, increased availability of a range of effective vaccines should provide assurance.

At least seven vaccines are likely to be available later this year. In the meantime, there is a remarkable know-how in place, so the current stable can be tweaked quickly, if required. In addition, mRNA vaccines made by Pfizer-BioNTech and Moderna are much easier to adjust than traditional vaccine technologies.

Not every variant demands a new vaccine, as vaccines produce a broad immune response that will cover many mutations. But if variants continue to cause trouble, there is a likelihood that booster shots may be needed. – Additional reporting: Guardian

Kevin O'Sullivan

Kevin O'Sullivan

Kevin O'Sullivan is Environment and Science Editor and former editor of The Irish Times