Monitoring SARS-CoV-2 variants with complementary surveillance systems: risk evaluation of the Omicron JN.1 variant in France, August 2023 to January 2024

Eurosurveillance

Adriana Traore, Kelly Charniga, Sophie Grellet, Garance Terpant, Héléna Da Cruz, Anais Lamy, Nathalie Thomas, Gwladys Gbaguidi, Alizé Mercier, Julie Prudhomme, Benoit Visseaux, Vincent Vieillefond, Stéphanie Haim-Boukobza, Jean-Marc Giannoli, RELAB Study Group, Laboratory group, Javier Castro-Alvarez, Alain-Claude Kouamen, Marie-Anne Rameix-Welti, Samar Beirrera-Ibraim, Gregory Destras, Laurence Josset^, Simon Cauchemez, Bruno Lina, Bruno Coignard, Justine Schaeffer, Vincent Enouf, Antonin Bal

Key public health message

What did you want to address in this study and why?

SARS-CoV-2, the virus causing COVID-19, is constantly evolving. It remains essential to monitor SARS-CoV-2 variants and evaluate their potential impact. In August 2023, a new variant named BA.2.86 raised concerns in France, as it was genetically very different from other variants circulating at the time. We reinforced epidemiological and clinical surveillance of BA.2.86 and its sub-lineage JN.1 to evaluate the need for dedicated control measures.

What have we learnt from this study?

The diversity of data sources from our routine surveillance system allowed us to detect and monitor emergence of BA.2.86 and JN.1 early and to obtain accurate and useful data. We collaborated with a modelling team to study the spread of these new variants in France and initiated targeted investigations of BA.2.86 cases, in collaboration with a new network of community-based laboratories RELAB to gather more information on a public health signal.

What are the implications of your findings for public health?

This study found no evidence of increased public health impact of JN.1 compared with previously circulating variants, despite its genetic differences. In addition, we showed the benefit of combining various surveillance systems and complementary investigations that can be triggered on-demand. The data obtained from the novel network of community-based laboratories (RELAB network) proved to be useful for respiratory virus surveillance.

More information at DOI: https://doi.org/10.2807/1560-7917.ES.2025.30.1.2400293