Study reveals significant post-COVID meningitis resurgence

A team of scientists from the Institut Pasteur has used the database of the National Reference Center for Meningococci to trace the evolution of invasive meningococcal disease cases in France between 2015 and 2022, revealing an unprecedented resurgence within the disease after the easing of control measures imposed through the COVID-19 epidemic. Recently reported cases have mainly been attributable to meningococcal serogroups that were less frequent before the pandemic, and there was a selected uptick in cases amongst people aged 16 to 24. The outcomes, published within the Journal of Infection and Public Health on October 12, 2023, should help guide adaptation of the vaccine strategy for this fatal disease.

In the course of the COVID-19 epidemic, health and hygiene measures like wearing masks and social distancing had a positive impact on respiratory infections. This was the case for invasive meningococcal disease (IMD), with the variety of infections falling by greater than 75% in 2020 and 2021. But what would occur at the top of the pandemic, when the protective measures were eased?

In the course of the COVID-19 pandemic, two theories emerged. The primary was that this positive effect would last and that meningococci would stop circulating over the long run. The second was that there can be a rapid resurgence in bacterial activity amongst a naive population which had not come into contact with the bacteria for a very long time.”

Muhamed-Kheir Taha, co-lead creator of the study, Head of the Invasive Bacterial Infections Unit and Director of the National Reference Center for Meningococci on the Institut Pasteur

A team of scientists from the Institut Pasteur due to this fact decided to conduct an in depth study of the evolution of the disease between 2015 and 2022, they usually confirmed the second hypothesis.

Using samples from the National Reference Center for Meningococci, which has recorded all cases of IMD in France since 1980, the scientists were in a position to look back over the pandemic period. The primary remark was clear. “There was an unprecedented resurgence in invasive meningococcal disease in autumn 2022, and now, in autumn 2023, the variety of cases is higher than within the pre-COVID-19 period,” outlines Samy Taha, first creator of the study and a scientist within the Institut Pasteur’s Invasive Bacterial Infections Unit. Compared with a complete of 298 cases recorded between January and September 2019, 421 cases have already been recorded between January and September 2023 – an increase of 36%, though the winter peak has not yet arrived. The figure for a similar period in 2021 was 53 cases. There are two essential explanations for this: general immunity was weaker because strains were circulating less, but there was also a decrease in vaccination, with meningitis C vaccination falling by 20% through the first lockdown, for instance. So the population has turn out to be naive when faced with bacteria which might be always evolving – the bacterial genome is very variable.

“Because the pandemic, there was a selected resurgence in meningococcal serogroups W and Y compared with the opposite serogroups,” continues Ala-Eddine Deghmane, co-lead creator of the study and Deputy Director of the National Reference Center for Meningococci on the Institut Pasteur. “And although all age groups are concerned, we found that those most affected by this recent wave of meningitis are young people aged 16 to 24.” In other words, the meningococcal bacterial strains liable for IMD today are different from people who were circulating before the pandemic, they usually goal different age groups. “It is nearly as if the COVID-19 epidemic has reset your entire system,” says Samy Taha.

This resurgence in meningitis could gather momentum in the approaching months with the effect of seasonal influenza. The influenza virus creates a positive context for the event of meningococcal bacteria. All mass gatherings is usually a risk factor for infection on the whole, and particularly for IMD.

In France, only meningitis C vaccination is mandatory; vaccination for meningitis B is merely really helpful in infants. But there are usually not yet any recommendations in the overall population for serogroups Y and W. The scientists are due to this fact involved with the French National Authority for Health to assist adapt the longer term vaccine strategy. “If the quadrivalent meningococcal vaccine for serogroups A, C, Y and W were to be really helpful for adolescents, it would supply direct protection for them and likewise indirect protection for other categories of the population,” explains Ala-Eddine Deghmane. Adolescents are the essential healthy carriers of meningococci. “We must keep in mind that without treatment, the mortality rate for bacterial meningitis is virtually 100%. Even with proper treatment, there continues to be a ten% mortality rate. So vaccine prevention is crucial,” concludes Muhamed-Kheir Taha.