Lancet study decodes what’s behind EG.5.1’s rapid spread

LONDON: The highly transmissible Covid sub-varaint EG.5, dubbed as Eris, is spreading rapidly across the globe because of its ability to escape from antibodies, finds a study.

Since May 2023, the EG.5 lineage of SARS-CoV-2, known as Eris, has been spreading globally and was classified as a Variant of Interest by the World Health Organization (WHO) in early August.

It is the most prevalent Covid variant in the US, UK and other countries. However, the cause of the increasing spread of Eris has been unclear.

Scientists from the German Primate Center-Leibniz Institute for Primate Research in Gottingen in Germany, have now examined the characteristics of the Eris sublineage EG.5.1.

The researchers found that EG.5.1 is not more infectious than its predecessors, meaning it cannot infect host cells more effectively.

However, EG.5.1 can escape neutralising antibodies better than other currently circulating SARS-CoV-2 lineages, giving it an advantage in infecting individuals whose immune systems have produced neutralising antibodies after vaccination or infection. The findings are published in The Lancet Infectious Diseases.

There is, however, currently no evidence to suggest that infections with EG.5 and EG.5.1 are leading to more severe illnesses.

"We have found evidence that an increased ability to escape from antibodies is the likely cause for the enhanced spread of Eris," said Markus Hoffmann, the leading scientist behind the study.

"We tested how effectively the Eris sublineage EG.5.1 can enter host cells and how efficiently it is neutralised by antibodies in the blood of vaccinated individuals without a SARS-CoV-2 infection and those with a SARS-CoV-2 infection. During this process, we found that, in comparison to other currently circulating SARS-CoV-2 lineages, EG.5.1 does not possess an advantage in infecting host cells.

In experiments conducted using replication-incompetent viruses produced in the laboratory, known as pseudoviruses, the team found that EG.5.1 is less effectively neutralised by antibodies present in the blood of vaccinated individuals or vaccinated and infected individuals.

"In summary, our results suggest that the spread of EG.5 and its sub-lineages primarily relies on antibody escape rather than an enhanced ability to infect host cells. However, the increase in the ability to escape antibodies is rather moderate and by no means sufficient to completely undermine our immunity that has been established through vaccination or prior infection," Hoffmann said.

Further, the researchers also noted that the newly adapted Covid vaccines based on the widespread XBB.1.5 will also be effective against EG.5 and its sublineages.

"Since Eris is a descendant of the closely related XBB.1.9 lineage, and the various XBB sublineages exhibit only minor differences among themselves, it can be assumed that the newly adapted vaccines will also be effective against EG.5 and its sub-lineages. Primary and booster vaccination, especially for high-risk groups and their close contacts, are therefore advisable," said Stefan Pohlmann, Head of the Infection Biology Unit at the Centre.