Invasive meningococcal infections in France in 2022 (Sante publique France, October 16, 2023)

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Invasive meningococcal infections in France in 2022


Published on October 16, 2023
Updated on October 16, 2023

Key points

• Notable evolution in the epidemiology of invasive meningococcal infections (IIM) in 2022 after two years of low incidence, with in particular:
  • An early and high peak in the number of IIM cases in December 2022;
  • A marked increase in IIM Y and W compared to the pre-COVID-19 pandemic period;
  • Heterogeneity in the age of cases depending on the serogroup, with in particular a significant proportion of IIM B and W in infants, IIM B and Y in 15-24 year olds, and IIM Y and W in 60 year olds and more ;
  • The emergence of strains causing epidemic phenomena and hyperendemia of IIM B among young adults in certain regions;
  • A modified clonal diversity with in particular the expansion of the W strains of ST-9316 which had been described in Hauts de France between 2015 and 2018;
  • Higher lethality of IIM W compared to other serogroups, partly linked to the expansion of ST-9316 strains;
  • The very low incidence of IIM C with the probable establishment of group immunity linked to the gradual increase in vaccination coverage among adolescents which must be maintained over time.
• The marked resurgence of IIM could be explained by the resumption of transmission of meningococci in a population with reduced immunity given less exposure to meningococci during the COVID-19 period, in a context of concomitant epidemics of respiratory viral infections at the end of 2022.
• The meningococcal vaccination strategy will soon be re-evaluated by the High Authority of Health (HAS) based on recent developments in the epidemiology of IIMs.

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​https://www.santepubliquefrance.fr/...ns-invasives-a-meningocoque-en-france-en-2022

 

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A SIGNIFICANT “POST-COVID” REBOUND IN MENINGOCOCCAL MENINGITIS​

Bacterial Infections Unit.​

PRESS RELEASE

14.11.2023

Thanks to the database of the National Reference Center for Meningococci, a team of scientists from the Pasteur Institute was able to trace the evolution of cases of meningococcal meningitis in France between 2015 and 2022 and highlight an unprecedented rebound in the disease after the cessation of health measures put in place during the Covid-19 epidemic. If the new cases reported are mainly linked to groups of meningococci which were less frequent before the pandemic, they also now concern more 16-24 year olds. Results published in the Journal of Infection and Public Health on October 12, 2023, which should help adapt the vaccination strategy for this deadly disease.

During the Covid-19 epidemic, barrier gestures such as wearing a mask and social distancing had positive consequences on respiratory infections. This was the case for meningococcal meningitis, which saw its number of contaminations drop by more than 75% in 2020 and 2021. But what would happen at the end of the pandemic, when protective measures eased? ? “ During the Covid-19 pandemic, two hypotheses emerged ,” recalls Muhamed-Kheir Taha, co-lead author of the study and head of the Invasive Bacterial Infections Unit and the National Reference Center for Meningococci at the Institut Pasteur . The first was to say that this positive effect would last, and that the meningococcus would stop circulating in the long term. The second hypothesis was in the direction of a rapid resumption of the activity of the bacteria in the face of a naive population, which had no longer been in contact with them for a long period . This is how a team of scientists from the Pasteur Institute decided to closely study the evolution of the disease between 2015 and 2022, and confirmed the second hypothesis.

Thanks to samples from the National Meningococcal Reference Center – which lists all cases of meningococcal meningitis in France since 1980 – the researchers were able to revisit this period of pandemic. The first observation was clear. “ Meningococcal meningitis experienced an unprecedented rebound in the fall of 2022, with today, in the fall of 2023, a number of cases higher than the period which preceded the Covid-19 pandemic,” summarizes Samy Taha , first author of the study and researcher in the Invasive Bacterial Infections Unit at the Institut Pasteur. If 298 cases were recorded between January and September 2019, 421 cases have already been recorded between January and September 2023, an increase of 36% in cases, even though the winter peak has not yet occurred. This figure was 53 cases for the same period in 2021. There are two main explanations for this: a decrease in general immunity following the reduction in the circulation of strains, but also the drop in vaccination, which fell by 20% for vaccination against meningococcus C during the first confinement for example. Thus the population has once again become naive in the face of constantly evolving bacteria, their genome being particularly variable.

“ Moreover, meningococci of groups W and Y appeared much more numerous than the others after the pandemic ,” continues Ala-Eddine Deghmane, co-senior author of the study and deputy head of the National Reference Center for Meningococci at the Pastor Institute. And if all age categories are affected, it turns out that those most affected by this new wave of meningitis are young people aged 16 to 24. ” In other words, the bacterial strains of meningococci today responsible for meningitis are no longer the same as those circulating before the pandemic and they target more different age groups. “ It’s a bit as if, with the Covid-19 epidemic, the whole system had been reset. », illustrates Samy Taha.

This resurgence of meningitis could well increase in the months to come with the seasonal flu epidemic. Indeed, the influenza virus creates a favorable context for the development of meningococcal bacteria. Furthermore, all large gatherings are conducive to contamination in general and to the spread of meningococcal meningitis in particular.

Today in France, only vaccination against meningococcus group C is obligatory, vaccination against meningococcus B being simply recommended in infants. But there are not yet any recommendations for the general population against groups Y and W. Researchers are therefore in contact with the High Health Authority to help adapt the future vaccination strategy. “ If the tetravalent vaccine targeting group A, C, Y and W meningococci was recommended for adolescents, this would protect them directly but also indirectly protect other categories of the population. », underlines Ala-Eddine Deghmane. Adolescents are in fact the first healthy carriers of meningococcus. “ And we must not forget that without treatment, bacterial meningitis is almost 100% fatal and even when properly treated, mortality remains 10%. This underlines the importance of vaccination prevention. », concludes Muhamed-Kheir Taha.

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Source :

The rapid rebound of invasive meningococcal disease in France at the end of 2022, Journal of Infection and Public Health , October 12, 2023
Samy Taha, Eva Hong, Mélanie Denizon, Michael Falguières, Aude Terrade, Ala-Eddine Deghmane, Muhamed-Kheir Taha
Invasive Bacterial Infections Unit and National Reference Center for Meningococci and Haemophilus influnezae, Institut Pasteur, Université Paris Cité, France
https://doi.org/10.1016/j.jiph.2023.10.001


​https://www.pasteur.fr/fr/espace-pr...ant-rebond-post-covid-meningite-meningocoques