In recent days, scientists have started to raise concerns about a new coronavirus variant that was first detected in someone who had travelled to Hong Kong from South Africa.

One expert described it as “horrific”, while a senior member of the UK Health Security Agency said it was “the worst variant we have seen so far”.

And last night, the UK government announced six countries in southern Africa would be added to the red list.

So could the new variant render current vaccines obsolete? Is it more transmissible or more severe than previous versions of the virus? And could a possible wave of infections be worse than Delta?

Scientists are urging caution while we gather new evidence.

Let’s take a look at what we know – and what we don’t know – so far.

Vaccines still “likely” to give high protection against hospitalisation and death

Part of the reason some experts are worried about this new variant – currently referred to as “B.1.1.529” – is because it has an “unprecedented” number of mutations.

Mutations in any virus are normal as the pathogen spreads – some might end up being helpful to the virus, while others may cause it to die off.

What is of concern in this case is the high number of mutations on the “spike protein” – the part of the virus that interacts with human cells.

In theory, this could help the virus get round the body’s defences, even in people who have been previously infected with another variant of coronavirus or have been vaccinated. This is called “immune escape”.

Vaccine efficacy is measured on a sliding scale, rather than a simple “works” vs “doesn’t work” binary. That’s why we talk about efficacy in percentage terms – for example, the Pfizer vaccine cuts the risk of hospitalisation from the Delta variant by 96 per cent, and AstraZeneca by 92 per cent.

So the key question is: could this latest variant reduce the efficacy of the vaccines, and if so, by how much?

For now, we don’t have real-world data on whether and how the new variant responds to the vaccine, so scientists can’t yet put a figure on the extent of immune escape it might cause.

Nevertheless, the South African National Institute for Communicable Diseases said last night that, based on its understanding of this variant’s mutations, “partial immune escape is likely, but it is likely that vaccines will still offer high levels of protection against hospitalisation and death”.

Does the variant spread more easily?

The data we have so far on the spread of this new variant in South Africa can’t answer this question definitively.

But, says Sharon Peacock, professor of public health at the University of Cambridge, “initial observations suggest that B.1.1.529 was able to become established in Gauteng province [in South Africa] and outcompete Delta”. (Outcompeting another virus tends to mean it’s more easily spread).

There are, Professor Peacock says, “several explanations for this”. It could be that a large super-spreader event has taken place in Gauteng and this has given “the impression of outcompeting Delta”. In other words, what looks like a generalised rise in cases of the new variant across the province could be a quirk in the data caused by a one-off incident.

But she warns, “the other explanation is that B.1.1.529 can actually outcompete Delta”.

“In summary,” Professor Peacock says, “the full significance of this variant is not known.”

Does it cause more severe illness?

Again, we don’t have clear data on this yet. Francois Balloux, professor of computational statistics biology at University College London, says any prediction on this question “feels premature”.

Possible new variant wave “should be far less painful” than Delta

We don’t know yet whether we’ll see a new wave of infections caused by this variant.

But if we do, Professor Balloux offers a note of cautious optimism: “With high vaccination rates and promising drugs on the horizon, a possible B.1.1.529 wave should be far less painful to weather than the alpha and delta ones.”