New Delhi, March 19 : The latest set of Covid-19 vaccines offered no increased protection against the JN.1 variant, which continues to circulate, according to a study.

JN.1, from the lineage of Omicron, is an off-spin of BA.2.86.

The variant, first detected in Luxembourg in August, was classified as a variant of interest (VOI) by the World Health Organisation (WHO) due to its rapid spread.

The additional mutation L455S in the spike protein of JN.1 is believed to have provided the variant with immune-evasion properties.

The study, appearing on a preprint site and not peer-reviewed yet, examined the efficacy of XBB 1.5 boosters on the JN.1 variant among 76 people. The findings showed that the vaccine provided better coverage overall, but the globally dominant JN.1 managed to evade them.

"Remarkably, while many individual mutations that emerged between 2020 and 2022 exhibit escape from sera following primary vaccination, few escape boosted sera," said Alejandro B. Balazs, from Ragon Institute of Massachusetts General Hospital, in the paper.

"An updated XBB.1.5 booster significantly increased titers against newer variants but not JN.1," he added.

Importantly, the team also found that newly emerging Covid variants have 'more efficient ways of entering cells", besides the common entry point - ACE2.

"In addition to escape from vaccine sera, we found that mutations also contribute significantly to the ability of pseudovirus to infect cells, suggesting that variant selection is optimising both antibody escape and viral entry. We found that spikes from variants post BA.1 produced pseudoviruses that were up to 30-fold better at transducing target cells than wild-type, suggesting that WT SARS-CoV-2 spike was not optimally configured for ACE2-dependent viral entry," the team said.

Although seasonal boosters improve immunity against new strains, the immune escape potential of the "variants demonstrate the need for novel approaches to adequately control SARS-CoV-2 transmission", the team said.

/IANS