Scientists have identified a previously unknown mutant strain in a fully vaccinated person who tested positive after returning from a short three-day trip to Cameroon.

Academics based at the IHU Mediterranee Infection in Marseille, France, discovered the new variant on December 10. So far, the variant doesn’t appear to be spreading rapidly and the World Health Organization has not yet labeled it a variant of concern. Nevertheless, researchers are still describing and keeping an eye on it.

The discovery of the B.1.640.2 mutation, dubbed IHU, was announced in the preprint server medRxiv, in a paper still awaiting peer review. Results show that IHU’s spike protein, the part of the virus responsible for invading host cells, carries the E484K mutation, which increases vaccine resistance. The genomic sequencing also revealed the N501Y mutation — first seen in the Alpha variant — that experts believe can make COVID-19 more transmissible.  

In the paper, the clinicians highlight that it’s important to keep our guard and expect more surprises from the virus: “These observations show once again the unpredictability of the emergence of new SARS-CoV-2 variants and their introduction from abroad,” they write. For comparison Omicron (B.1.1.529) carries around 50 mutations and appears to be better at infecting people who already have a level of immunity. Thankfully, a growing body of research proves it is also less likely to trigger severe symptoms.

Like many countries in Europe, France is experiencing a surge in the number of cases due to the Omicron variant.

Experts insist that IHU, which predates Omicron but has yet to cause widespread harm, should not cause concern – predicting that it may fade into the background. In an interview with the Daily Mail, Dr. Thomas Peacock, a virologist at Imperial College London, said the mutation had “a decent chance to cause trouble but never really materialized. So it is definitely not one worth worrying about too much at the moment.”

The strain was first uploaded to a variant tracking database on November 4, more than two weeks before Omicron was sequenced. For comparison, French authorities are now reporting over 300,000 new cases a day thought to be mostly Omicron, with data suggesting that the researchers have identified only 12 cases of IHU over the same period. 

On the whole, France has good surveillance for COVID-19 variants, meaning health professionals quickly pinpoint any new mutant strains. In contrast to Britain, which only checks three in ten cases for variants. The paper’s authors state that the emergence of the new variant emphasizes the importance of regular “genomic surveillance” on a countrywide scale.