Omicron has spawned yet another sub-variant that appears to be more infectious and capable of evading existing immunity than many of those that have come before it.
Globally, the EG.5 variant – nicknamed “Eris” after the Greek goddess of strife and discord – is steadily growing in prevalence, but there’s currently no sign that it causes more severe disease.
Here’s what we know so far.
Bears similarities to XBB.1.5
EG.5 is another form of the Omicron COVID-19 variant, which contains many of the same mutations as XBB.1.5 – sometimes referred to as the “Kraken” variant, according to an analysis by Gavi, the Vaccine Alliance.
A key difference is that EG.5 carries an additional F456L amino acid mutation in the spike protein that sits on the surface of the virus.
Preliminary evidence suggests that this might help EG.5 to evade neutralisation by antibodies in body fluids, even if someone has previously been infected with one of the previously circulating XBB forms of Omicron. It also has a spike protein mutation called Q52H, the implications of which are unknown.
According to Eric Topol, Professor of Molecular Medicine and director of the Scripps Translational Science Institute in La Jolla, California, EG.5 is likely to have emerged because of the widespread use of monoclonal antibodies to treat COVID-19 infections.
Though effective, these drugs can inadvertently drive the development of viruses with altered properties, because viruses carrying additional mutations are more likely survive and infect other people.
Circulating since February 2023
EG.5 was first reported on February 17, and on July 19, was designated as a ‘variant under monitoring’ – one with genetic changes suspected to affect the way it behaves and with early signals of faster spread.
As of August 7, EG.5 had been detected in 51 countries across Asia, North America, Australia, and Europe, although regional differences in surveillance may mean it is circulating elsewhere as well.
During the week ending 23 July 2023, the global prevalence of EG.5 was 17.4 percent.
“This is a notable rise from the data reported four weeks prior, when the global prevalence of EG.5 was 7.6 percent,” WHO said.
The WHO has now upgraded EG.5 to a ‘variant of interest’
EG.5 was upgraded to a variant of interest (VOI), one containing genetic changes predicted or known to affect characteristics such as disease severity, transmissibility, or antibody evasion – on August 9.
VOIs must also have a growth advantage over other circulating variants in more than one WHO region, with evidence of increasing prevalence and an increasing number of cases over time, or some other evidence to suggest it poses an emerging risk to global public health.
However, based on the available evidence, WHO has assessed the global public health risk posed by EG.5 to be low, aligning with the risk associated with XBB.1.16 (nicknamed Arcturus) and the other currently circulating VOIs.
“While EG.5 has shown increased prevalence, growth advantage, and immune escape properties, there have been no reported changes in disease severity to date,” said WHO, adding that although an increase in hospitalisations has been observed in countries such as Japan and the Republic of Korea, these aren’t necessarily associated with EG.5.
Reinfections likely despite low risk
The ability of EG.5 to evade neutralisation with antibodies means people are more likely to be infected with it, even if they have previously been vaccinated against COVID-19 and infected with earlier versions of the Omicron variant. Neutralising antibodies are molecules that bind to viruses and destroy them before they get inside our cells and start replicating – so they are an important early line of defense against infection. However, previous exposure to Omicron and/or other SARS-CoV-2 variants makes it highly likely that other forms of immune defense, including T-cells, will recognise and destroy virus
COVID-19 vaccines can still protect
The ability of EG.5 to partially evade antibody neutralisation also means that COVID-19 vaccines are less likely to protect people against infection than they were against earlier SARS-CoV-2 variants such as Alpha or Delta.
Levels of antibodies are also known to wane in the months following vaccination. However, if you have been fully vaccinated against COVID-19, your body’s immune cells will mount a faster and stronger immune response against EG.5, than if you hadn’t been vaccinated, making severe disease, hospitalisation or death much less likely.
Booster vaccinations will also top up your antibody levels and make you less susceptible to infection, so if you are eligible to receive one, it is important to take up this offer – particularly if you are more susceptible to severe COVID-19 due to your age or other underlying health conditions.
Updated COVID-19 boosters, expected to be available within the coming months, will not target EG.5 specifically, but are based on XBB.1.5. Its similarity to EG.5 means they are still likely to offer decent protection against it.