Significant 'post-COVID' rise in invasive meningococcal illness is found in the study.

 Significant 'post-COVID' rise in invasive meningococcal illness is found in the study.

Using the National Reference Center for Meningococci database, a group of scientists from Institut Pasteur have tracked the development of invasive meningococcal disease cases in France from 2015 to 2022. Their findings indicate an extraordinary return of the disease following the relaxation of control measures put in place during the COVID-19 pandemic.

Meningococcal serogroups that were less common prior to the pandemic have mostly been the cause of recently reported cases; individuals between the ages of 16 and 24 have seen an especially high incidence of cases. The findings, which were released in the Journal of Infection and Public Health, ought to direct modifications to the vaccination approach for this lethal illness.

Health and hygiene precautions including mask use and social separation helped reduce respiratory infections during the COVID-19 pandemic. Invasive meningococcal disease (IMD) was one example of this, with a more than 75% decrease in infections in 2020 and 2021. However, what would happen when the pandemic ended and the precautions were loosened?

Muhamed-Kheir Taha, co-lead author of the study, head of the Institut Pasteur's Invasive Bacterial Infections Unit and director of the National Reference Center for Meningococci, says, "During the COVID-19 pandemic, two theories emerged." "The first was that meningococci would eventually cease to circulate and that this beneficial effect would last. The second was that a naive population that had not been exposed to the germs in a long period would experience a sharp rise in bacterial activity."

Thus, a group of researchers at the Institut Pasteur made the decision to carry out an extensive analysis of the illness's development from 2015 to 2022, and they were able to verify the second theory.

The researchers looked back over the pandemic period using samples from the National Reference Center for Meningococci, which has kept track of all IMD cases in France since 1980. The first finding was evident.

First author Samy Taha, a scientist at Institut Pasteur's Invasive Bacterial Infections Unit, states, "There was an unprecedented resurgence in invasive meningococcal disease in autumn 2022, and now, in autumn 2023, the number of cases is higher than in the pre-COVID-19 period." Even though the winter season has not yet arrived, there have already been 421 occurrences reported between January and September 2023, a 36% increase from the 298 cases that were registered between January and September 2019.

53 cases were reported during the same time period in 2021. There are two main causes for this: first, there was a decline in vaccination rates, with meningitis C vaccination falling by 20% during the first lockdown, suggesting that general immunity was lower because strains were circulating less. Because the bacterial genome is so varied, the population has grown ignorant when faced with continually developing bacteria.

Co-lead author of the study and deputy director of the National Reference Center for Meningococci at the Institut Pasteur Ala-Eddine Deghmane adds, "Since the pandemic, there has been a particular resurgence in meningococcal serogroups W and Y compared with the other serogroups." "And although all age groups are concerned, we found that those most affected by this new wave of meningitis are young people aged 16 to 24."

Put differently, the age groups that are targeted by the meningococcal bacterial strains that cause IMD today differ from those that existed prior to the pandemic. "It is almost as if the COVID-19 epidemic has reset the entire system," states Samy Taha.

The effect of seasonal influenza may contribute to the recurrence of meningitis in the upcoming months. The influenza virus fosters an environment that is conducive to the growth of meningococcal bacteria. Any large-scale event may increase the chance of infection in general and IMD in particular.

Meningitis B vaccine for babies is only advised in France; meningitis C immunization is required. However, there are currently no recommendations for serogroups Y and W in the general population. In order to assist in modifying the next vaccination plan, the scientists have been in touch with the French National Authority for Health.

"If the quadrivalent meningococcal vaccine for serogroups A, C, Y and W were to be recommended for adolescents, it would provide direct protection for them and also indirect protection for other categories of the population," says Ala-Eddine Deghmane. The majority of healthy carriers of meningococci are adolescents. "We must keep in mind that the death rate from bacterial meningitis is over 100% in the absence of therapy. 10% of patients still die, even with appropriate care. Therefore, it is imperative to prevent vaccinations," says Muhamed-Kheir Taha.