How do scientists know the new UK variant is 70% more transmissible, and how certain are they of this figure?
Our gift to the world: the UK variant of Sars-CoV-2. There are sufficient data to quote 70% greater infectivity, but how was this figure ascertained?” D Moon, Brighton
This has been investigated using a number of different methods, all of which lead to the same basic conclusion, that the new B117 variant is easier to pass from person to person – even if the precise increase in transmissibility is only an estimate, for now.
One method involved comparing the growth in cases of the new variant and old variant within the same population, which enabled researchers to control other factors that can affect rates of transmission, such as social distancing. They also followed the pattern of signals in Covid tests across the UK, looking at the increase in cases of “S gene dropout” caused by specific mutations in the viral spike protein – a proxy for the new variant.
“Both of these methods show that the new variant replaced the older variants in the UK population, strongly suggesting that the new variant is a fitter virus and most likely achieved this though increased transmissibility,” said Paul Kellam, a professor of virus genomics at Imperial College London.
The researchers also tested various mathematical models to see which one best fitted the observed increase in the new variant, and discovered that it would be consistent with an increase in the reproduction number of 0.4 to 0.7.
“What we would still like to see is proof in animal models of transmission that the new variant is better at establishing new infections than the old variant. But for now the evidence is sufficiently compelling that we must act on it, which is why we have entered another lockdown,” Kellam said.
What does a 70% increase in transmissibility actually mean?
Does it mean that if you breathe in a small viral load you are 70% more likely to catch it, or perhaps that you need to socially distance 70% further?” Brian, retired IT consultant, Reading
The 70% figure derives from this estimated increase in the R value of 0.4 to 0.7. Say the old variant was spreading at an R of 1.5, meaning 10 Covid-positive people transmitted infection to 15 new people: “The new variant would have a R of 1.9 to 2.3, so 10 people with Covid-19 would transmit infection to 19 to 23 new people,” said Kellam. “It is reasonable to say that strict adherence to the rules that are designed to break chains of transmission (hands, face and space) are still effective, but that the tolerance for bending or ignoring the rules may be much less, as we cannot discount that multiple factors have contributed to the increase in transmission, including poor adherence to tier rules.”
Can I be reinfected with the new variant if I’ve already had Covid?
Can people who have had Covid catch this new variant as well? James Crawford, Covid swabber, Bristol
This is an area of active research. Although there have been reports of people being reinfected with older coronavirus variants, such reinfections appear to be rare. “What we know about the new UK variant at the moment strongly suggests that it remains sensitive to the immune response of the older variants and will be similarly sensitive to the immune response generated by the two vaccines currently being rolled out in the UK,” said Kellam.
Are surfaces likely to play a greater role in transmission of the new variant?
Do I need to up my game regarding cleaning?” Natasha, Cumbria
This is also unclear. However, if the new variant finds it easier to bind to and infect cells, which is one theory being investigated, this could mean a smaller number of viral particles is needed to establish an infection. Complying with the guidance on hands, face and space is therefore more important than ever: 70% more handwashing will not compensate for not wearing a mask.
How did the mutation happen, and why did it happen in the UK?
If the mutation occurs when the virus is transmitted from one person to another, surely the persistently high number of infections in this country will give the virus more opportunity to further mutate, the possible result being this devastating world pandemic is prolonged whilst new vaccines are developed.” Steven Cooper, retired engineer, Herefordshire
Viruses are constantly acquiring small changes in their genetic code. Usually, these “mutations” have no effect, but occasionally they will alter how the virus behaves – which is what may have happened with the B117 and South African variants. These are far from being the only coronavirus variants in circulation, but they’re generating concern because the mutations they carry may make them more infectious.
As for how – and where – the B117 variant arose, it could simply be that Britain was the first country to detect it, as we routinely sequence more viral genomes than many other countries. Also being explored is whether mutations are more likely to arise in patients with long-running coronavirus infections who are treated with blood from recovered Covid-19 patients (convalescent plasma). One study, which followed a single immunocompromised patient, detected important changes in the virus each time the patient received plasma treatment, raising the possibility that the antibodies it contained placed additional pressure on the virus to mutate. However, this is less likely to happen in people with healthier immune systems.
Will the Covid-19 vaccines still work, and, if not, how would scientists go about updating them?
Yesterday, I got the first shot of the Moderna vaccine, am I covered from the new variant?” Conor, laboratory worker, New York
Most scientists are confident that current Covid-19 vaccines will protect against the new B117 variant, but there’s a risk that they may become less effective if the virus continues to mutate. This is another reason why it’s important to reduce the number of people who become infected – because mutations are more likely to occur when the virus infects new hosts.
If the vaccines did become less effective, they would be relatively easy to tweak – especially those based on RNA and vector vaccines, including the Pfizer/BioNTech and Oxford/AstraZeneca vaccines. Doing so would involve making small changes to the sequence of the genetic material these vaccines contain, and could be incorporated in the new design within a matter of days, said Brendan Wren, a professor of vaccinology at the London School of Hygiene & Tropical Medicine, who added: “I’m sure that the Oxford group have already modified their vaccine design to include variants as they arise.”
Can young (primary age) children be infected with the new variant/s and pass it on to their friends and parents?
How much do schools contribute to the spread of Covid, and how has that changed since the emergence of the new variant?” Olivia Bacon, clinical scientist, Hampshire
People of all ages can be infected with both the new and old coronavirus variants and transmit them to other people, but primary-aged children appear less likely to do so – at least where the older variants are concerned. Whether this also holds true for the new B117 variant is still uncertain. “It is most likely that the B117 lineage influences transmissibility in all age groups, and there is not yet clear evidence that the degree to which transmission has increased in children is any different than the degree to which it has increased in adults,” said Erik Volz at Imperial College London, who is studying the new variant.
Even if the variant is less transmissible between children than adults, the fact that transmission does occur is still a major concern when there are such high case numbers and hospitals are under such stress – which is why schools are closed.
The new UK Covid variant: your questions answered The British Journal Editors and Wire Services/ The Guardian.