Global rollout must put in sprint to the line to see off delta variant risk

For much of the past fortnight many of us have been captivated by exhilarating action from Tokyo, as athletes at the peak of their careers and physical fitness battle for an elusive Olympic gold.

But scientists across the globe remain absorbed in a separate race: the fight between vaccines and variants.

By this point, we all know that viruses mutate. As they replicate, small “copying errors” creep into the genetic code – most have little consequence. But occasionally a mutation will be beneficial; it might make it slightly easier for the virus to enter human cells, or to avoid existing antibodies.

The most advantageous of these mutations are passed on and eventually become part of the virus’s default genome: a new, “fitter” variant has emerged. This process can happen as SARS-CoV-2 spreads or in one person.

Scientists say the virus used “Patient S”, the world’s longest Covid sufferer, as a “gym” to get fitter – mutating 40 times over 11 months.

According to the latest tranche of papers from the Government’s scientific advisory group for emergencies (Sage), it is new variants which present the “biggest longer-term threat to the UK’s health security”.

There are three key elements to look out for, the minutes add: a variant which is more infectious, causes more severe illness, or can escape prior immunity – plus, in the worst case, a combination of all three.

According to Sage, given our high vaccination rates, a vaccine-evading variant would be of most concern for the UK. Worryingly, recent modelling published in Scientific Reports put Britain in the danger zone, warning the combination of high case rates and high vaccination rates is conducive for the emergence of a variant with “extreme resistance training”.

“When most people are vaccinated, the vaccine resistant strain has an advantage over the original strain,” says Prof Fyodor Kondrashov, an expert in evolutionary genomics at the Institute of Science and Technology Austria and co-author of the report. “This means that the vaccine resistant strain spreads through the population faster than the original strain at a time when most people are vaccinated.”

Prof Jonathan Ball, a virologist at the University of Nottingham, adds that this can happen even where the vaccineevasive strain is less infectious.

“Think of it a bit like a see-saw, with immunity on one side and replication fitness [transmissibility] on the other,” he says. “The virus has to find what gives it an edge, and in a population with more immunity, an ‘escape variant’ might have that edge even if the overall fitness is reduced.”

Yet so far, in the tussle between vaccines and variants, the former is coming out on top, offering some hope that SARS-CoV-2 may struggle to render our defences useless.

Analysis by Public Health England, for instance, found two doses of either Pfizer or AstraZeneca remain 90 per cent effective against hospital admissions caused by the delta variant.

Even for beta – which contains the E484K mutation, thought to help the virus partially evade antibodies – realworld data from Qatar suggests Pfizer and Moderna are more than 95 per cent effective at preventing severe disease and death.

“If we think about defining what a well performing vaccine looks like, it’s one that’s breaking the link between infection, serious disease, hospitalisation and death,” says Prof Ball. “At the moment, the vaccines all seem to be holding up well against the variants that have emerged.”

And this is unlikely to change, some scientists argue, meaning another extremely contagious delta-like variant presents by far the greatest risk – it could take hold rapidly and, as no vaccine is 100 per cent effective, cause a substantial toll even in protected populations if case numbers grew high enough.

“I think the chances of a vaccineresistant strain emerging at all are negligible,” says Prof Angela Rasmussen, a virologist at the University of Saskatchewan in Canada. “It would require so many mutations in the spike protein that the virus wouldn’t ‘work’ anymore. It wouldn’t be able to replicate, because so many mutations would be required that they would disrupt parts of the virus needed for the virus to carry out its normal functions.”

Another delta-style variant, by contrast, is far from an underdog. Viruses, after all, exist to replicate.

But what Prof Rasmussen and the Sage scientists have in common is the race-plan. To finish the marathon on top, quell the threat of new variants and “reduce the risk to the UK”, the global vaccination rollout must proceed at record breaking speed.

‘At the moment, the vaccines all seem to be holding up well against the variants that have emerged’