We don’t know if the ‘Nigerian variant’ is more deadly

21 April 2021
What was claimed

The so-called “Nigerian variant” of Covid-19 is twice as deadly as the dominant “Kent variant”.

Our verdict

This reflects the number of deaths among the small number of cases from the “Nigerian variant” detected so far. At the time of writing there is not enough data to know whether this variant is more deadly or not.

The data in this piece is correct as of the time of publishing, on 21 April 2021.

Articles from news outlets, and posts on social media have raised concerns about the risk posed by a Covid-19 variant which has been dubbed the “Nigerian variant” (although evidence now suggests that the variant was first detected in the UK). It is officially known as  B1.525, or VUI202102/03 by Public Health England (PHE).

Kent Live reported that this strain kills “twice as many people” as other variants, claiming that it has “so far” killed 4.3% of the people it has infected. This is compared with 2.3% of infected people being killed by the Kent variant, which is now the most common strain in the UK.

This is misleading, because we don’t know the true number of people so far infected by either variant. Instead, these death rates are based on the number of deaths occurring among detected cases—and only 328 cases of the B1.525 variant have been found so far, which makes it hard to be confident about how deadly it is.  Public Health England (PHE) said in February there was no evidence that this variant causes more severe illness or increased transmissibility.

Kent Live also reported on concerns that this strain may be better at evading the protection of vaccines because it carries the E484K mutation. This mutation impacts the ‘spike protein’ on the outside of the SARS-CoV-2 virus (which causes Covid-19) which may help it to ‘slip past’ the body's immune system. This has been demonstrated in lab studies, but so far human studies have shown mixed results. 

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What is the B1.525 variant and how common is it? 

The variant has been recorded in at least 41 countries. It was first detected in the UK in December 2020 and, as of 15 April 2021, there have been 361 confirmed cases.

From figures up until the end of March, there had been 12 recorded deaths in the UK from this variant of Covid-19. 

PHE said in February: “There is currently no evidence that this set of mutations [in B1.525] causes more severe illness or increased transmissibility.”

At the time of writing, this variant of Covid-19 is classified as a “Variant under Investigation”. It possesses several genetic mutations, including the E484K spike protein mutation, which is present on a number of other variants. 

It is common for the genes of viruses to mutate over time, and most mutations make little difference.

A Variant of Concern is a genetic variant of Covid-19 which may present a bigger problem.

To be considered a Variant of Concern a variant must be associated with one or more of the following: 

  • an increase in transmissibility or other detrimental change in epidemiology
  • an increase in virulence or change in clinical disease presentation
  • escape from immunity derived from natural infection
  • a decrease in effectiveness of public health or clinical countermeasures, including vaccination, treatment in current clinical use, or testing if the impact is such that it is not easily mitigated by standard laboratory quality and regulatory measures

At the time of writing, the B1.525 variant has not met these criteria, and is classed instead as a Variant Under Investigation. This means it has mutations which may cause these problems, according to existing evidence, and there is evidence of community transmission of the variant in the UK or abroad.This may change following future risk assessments. 

Where do the comparative mortality figures come from? 

The reported figures come from a PHE report into the Covid-19 Variants of Concern and Under Investigation published on 1 April 2021. 

The report explains that the case fatality rate (proportion of deaths amongst confirmed cases) of variant B1.525 is 4.3%, compared with the ‘Kent’ variant which has a case fatality rate of 2.3%. 

Although from these numbers it appears fair to compare the case fatality rates between the two variants and conclude that B1.525 “kills twice as many people”, it is important to be aware of the context behind the two figures

The Kent variant (or B1.1.7) case fatality rate is based on 151, 344 cases and 3,504 deaths, whereas the rate for the B1.525 variant is based on 277 cases and 12 deaths recorded at the time. 

This is a much smaller number and means that the case fatality rate is much more likely to fluctuate even with small changes to the numbers of deaths. Percentages based on such small numbers are therefore very uncertain.

In addition, because we don’t know the true total number of people infected so far, these death rates are based on the number of deaths occurring among detected cases. This is another reason to treat these figures with caution. 

What about the vaccines? 

One of the mutations that the B1.525 variant carries is the E484K mutation which affects the “spike protein” on the virus surface. There is concern that this mutation may confer some resistance to the Covid-19 vaccines.

Lab studies have shown that antibodies are less able to react to variants with the E484K mutation. It is not certain, however, what degree of impact this will have in humans in the real world, and studies are ongoing.

Research is also underway to update current vaccine technology to make them more effective against the mutations.

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