How mutant Covid strains affect vaccine effectiveness

As the UK embarks on testing campaign, fears grow over Covid-19 mutations

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The UK government launched a door-to-door testing blitz on Tuesday amid fears that the virus strain first identified in South Africa could be spreading.

Authorities confirmed 43 cases of the virus in Bristol and Liverpool, in addition toto 11 cases detected on Monday.

Of greatest concern to scientists is that these 11 were not linked to overseas travel but were the result of the spike protein mutation E484K. In other words, the endemic UK strain of the virus is mutating into the South African strain, which is known to make vaccines less effective.

The UK and South African mutations are not the only strains to worry UK authorities. Earlier in January one of two Brazilian variants was detected.

The variant is distinct from strains that emerged in south-east England and South Africa but they share some key mutations.

One strain – the P1 variant – is understood to be more infectious than the other because it is able to better attach itself to human cells. This led to fears that it too can reduce vaccine effectiveness.

Strain first identified in South Africa known to reduce vaccine effectiveness

Scientists are preoccupied with the E484K South African mutation.

Last week Moderna revealed that lab studies showed that its vaccine-produced antibodies were six times less effective against the variant.

Novavax too reported that its vaccine was only 60 per cent effective against the South African strain compared with 85 per cent against the UK variant.

And foreboding news emerged on Tuesday courtesy of scientists from the University of Cambridge.

Tests into delaying the second dose of the Pfizer/BioNTech vaccine showed that elderly patients may be more at risk of infection from the South African variant with one dose failing to produce enough antibodies to overcome the virus.

So is the vaccine strategy in danger of failing?

At first take this might seem the case but reduced effectiveness is still significantly better than no effectiveness at all.

Results from Pfizer, Novavax, Jansen and Moderna show that their vaccines are still able to prevent many mild and moderate infections from the new variants.

They are also highly effective in warding off severe cases, hospital admissions and deaths – and it is this unholy trinity that needs to be tackled if coronavirus is to be defeated.

It should also be borne in mind that, like the virus itself, vaccines are mutable and so can be tweaked to tackle different strains.

This is not a simple task and would involve building a global surveillance network to monitor new variants and to determine how and when vaccines need to be adjusted.

The challenge is not insuperable, though, and last week executives from Moderna and Pfizer announced they were already considering new formulations to cope with mutations.

It could be that, like flu, every year vaccines will need to be altered to contend with Covid-19 variants. These adjustments could be made in a matter of weeks or months, so there is no prospect of a return to pandemic ground zero.

What does this mean for now?

In short, more of the same.

"Viruses cannot mutate if they can't replicate," Dr Anthony Fauci, head of the US National Institute of Allergy and Infectious Diseases, said on Monday.

His view was echoed on Tuesday by Dr Julian Tang of the University of Leicester, who told The Times that reducing contact rates is essential "to reduce the opportunities for viral spread and replication" and "to reduce the speed with which these different virus variants can evolve".

In England, the third lockdown appears to be taking effect with case numbers falling in recent days.


The news on Tuesday that the UK had administered more than 10 million vaccine doses, with only the US and China also reaching this mark, provides hope.

"If you stop [the variants] replication by vaccinating widely ... not only are you going to protect individuals from getting disease but you are going to prevent the emergence of variants," Dr Fauci said.