The variant of concern

The sun is shining as the UK comes out of its winter hibernation lockdown after a traumatic winter. Yet, despite a hugely successful vaccination campaign and a massive increase in testing, many people remain deeply concerned. Most of this concern surrounds variants to the Wild Type - the strain of the COVID-19 virus with no significant mutations.


There is good reason to be concerned about variants ("Variants of Concern"). The second wave of COVID-19 in the UK has been dominated by the B117 variant, which appears to have originated in Kent. Unlike the Wild Type, B117 is both more transmissible and causes more severe illness. In numbers:

  • without social distancing, each person infected with B117 is likely to infect 3-4 other people compared to 2-3 others for the Wild Type

  • for every 100 +80 years olds infected with B117, 82 will become critically ill, and 16 are likely to die compared to 50 and 10 for the Wild Type

More cases and more critically ill people means more pressure on the NHS, which has triggered the need for both of the major national lockdowns.


The positive news is that the first generation of COVID-19 vaccines is effective at reducing both:

  • people getting infected, which means they won't get sick or pass on the virus to others; and

  • people becoming critically ill or dying if they do get infected

These effects are good since they mean the risk of a third wave of COVID-19 is reduced, and the impact on the NHS is also reduced. Provided the UK continues its heroic vaccine rollout, and there is some social distancing over the next few months, we should see B117 pushed into submission - just don't plan on going to any big events.


Given that the B117 variant of COVID-19 is widespread in the UK and under some control, it is not a concern. So how much should we be concerned about other "variants"?


Since the pandemic started, there have been over 137 million reported cases of COVID-19 (certainly a vast underestimate of total actual cases). From this massive number of infections, there have been around 4,000 variants identified. Of these 4,000, only four are currently recognised as Variants of Concern in the UK (four more variants are "under investigation"). Two of these Variants of Concern are homegrown - B117 and B117 with the E484K mutation.*

The two other Variants of Concern are B1351 (South Africa) and P1 (Brazil). Much less evidence is available on these variants - this uncertainty in and of itself creates concern. But at the moment, neither of these variants appears more transmissible nor more deadly than B117. Current evidence also suggests that vaccinations effectively reduce the number of people who get critically ill or die after becoming infected with either of these variants. This impact is tentatively good news - see chart below, which is based on our modelling of the vaccine rollout and current evidence of the different variants.

Based on this evidence, some will conclude the pandemic is over. But for B1351, there is some early evidence to suggest that it can evade vaccinations and still infect people. This ability is terrible since it means the variant could spread through a vaccinated population as social distancing measures are relaxed. Even though fewer people would get critically sick for the same number of infections, there could be a large number of infections (remember that exponential growth quickly makes small numbers very large). The chart below shows this graphically for infectiousness (R0) and the impact of vaccinations - only the B1351 variant sits in the amber zone, meaning it may still spread after the vaccination programme.

The ability to evade vaccines is likely the main reason for surge testing in Lambeth and Wandsworth following an outbreak of at least 44 cases of B1351 at a care home.

The next few weeks will be critical for understanding B1351 in greater depth, specifically on how much it evades the current generation of vaccinations. It will also be essential in seeing how it progresses in the battle for COVID-19 dominance, which as the chart below shows, is a race currently being won by B117 (Kent).


------------ Sign up for our newsletter here. Published 14 April 2021

------------ * Some may be interested in whether we should be worried about other new variants. Without going into the genealogy (not my area) too much, there are a limited number of mutations that can benefit the SARS-CoV-2 virus. Consequently, as I understand there is likely to be a high degree of convergent evolution - this is why we have only variants coalescing around the same mutations.

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