By January, doctors at the Cedars-Sinai hospital in Los Angeles were detecting the variant in about half of all samples they tested, and the next month it accounted for 15 per cent of covid cases across the United States.
A recent study suggested Epsilon was more resistant to vaccines and other Covid treatments, so should we be concerned?
A Variant of Interest
The US’s Centers for Disease Prevention and Control (CDC) formally designated Epsilon a Variant of Concern as a result of this sudden spike in cases in California.
Preliminary research began to be published about the variant, suggesting it was approximately 20 per cent more transmissible than preceding strains of Covid.
Experts were concerned that the specific mutations in Epsilon included three in the spike protein – which the virus uses to attach to and enter other cells, and thus replicate itself.
It is the spike protein which mRNA Covid vaccines (such as Pfizer and Moderna) recreate in the body, training the immune system to produce antibodies and immune cells in response.
Therefore, if the Covid spike protein changes because of mutation, it is possible vaccination will become less effective at preventing subsequent infection.
As the variant began to be picked up in other countries around the world, the World Health Organisation (WHO) declared Epsilon to be a Variant of Interest – one step lower than the CDC designation – in early March.
How dangerous is Epsilon?
According to the CDC, as well as being slightly more transmissible, the Epsilon variant also has a “modest decrease in susceptibility” to a monoclonal antibody treatment for Covid, which has been given an emergency use authorisation in the US.
However, other antibody treatments are available, and after several months the CDC decided to downgrade Epsilon from a Variant of Concern to a Variant of Interest on 29 June because of increasing data that that the vaccines and other treatments were effective against it.
How widespread is it?
In February, Epsilon accounted for 16 per cent of all of America’s Covid samples tested, but this proved to be the peak for this variant.
Shortly afterwards the Alpha variant (first identified in Kent and known to be as much as 70 per cent more transmissible than previous Covid strains) took hold in the US and began to squeeze out Epsilon in the process.
By late June, just 1 per cent of samples tested in the US were of the Epsilon strain, prompting the CDC to downgrade it to a Variant of Interest.
It has never become widespread in the UK, with just 20 cases detected so far, according to GISAID (an international project which tracks and shares global data on viruses including Covid).
Public Health England have mentioned it in their last two reports on variants of concern and variants under investigation, however it has not yet been designated under either category and is only listed as being monitored for now.
The EU’s Centre for Disease Prevention and Control have listed Epsilon as a variant of interest but noted it is only sporadically being transmitted without the continent, largely from travellers from overseas bringing it in.
What does the latest research say?
A study from the University of Washington in the US was published last week into how Epsilon can evade vaccines to some extent.
Scientists found three mutations in the Epsilon coronavirus spike protein dampened the potency of antibodies in someone’s bloodstream, induced either by vaccines or having caught Covid in the past.
When the researchers tested the resilience of blood plasma from vaccinated people and those who had already had Covid, they found its ability to neutralise the Epsilon variant was reduced between 2 and 3.5 times.
“The mutations give this coronavirus variant of concern a means to totally evade specific monoclonal antibodies used in clinics and reduces the effectiveness of antibodies from the plasma of vaccinated people,” said the University of Washington’s School of Medicine.
However, because Epsilon is no longer especially prevalent, either globally or in the US where it first emerged, the variant is not feared to cause significant problems in effectiveness of vaccines.