Background

Invasive meningococcal infections have a high burden of disease, with a case-fatality rate of around 10%. In Belgium, the introduction of the MenC vaccine in 2002 led to a drastic fall in the number of invasive infections of this serotype.

Method

We used death certificates to assess meningococcal disease mortality in Belgium from 1993 to 2020. We included all deaths with an underlying cause of death with recorded International Classification of Diseases, 9th revision (ICD-9) codes 036.0–036.9 or ICD-10 codes A39.0–A39.9. Cases were analysed by sex, age group and province. Three distinct periods were defined: a pre-vaccination period (before 2002), a transition period during which the meningococcal C vaccine was introduced (2002-2003) and a post-vaccination period (from 2004). We calculated age-standardized mortality rates, using the standard EU population.

Results

Between 1993 and 2020, 395 deaths related to invasive meningococcal infection were recorded. The age-adjusted mortality rate was 0,20/100,000 inhabitants per year before the introduction of meningococcal C vaccination, 0,17/100,000 inhabitants per year during the transition period and 0,08/100,000 inhabitants per year during the post-vaccination period.

In the 3 periods, children aged <1 year were the most affected, with a mortality rate of 2,49/100,000 inhabitants (before 2002), 4,01/100,000 inhabitants (2002-2003) and 1,11/100,000 inhabitants (from 2004). The most common underlying causes of death were meningococcemia (62% of deaths), meningitis (17%) and Waterhouse-Friderichsen syndrome (WFS) (15%). The proportion of deaths linked to WFS fell sharply between the pre-vaccine (0.048 cases/100,000 inhabitants) and the post-vaccine period (0,006 cases/100,000 inhabitants).

Conclusion

The observed decline in mortality rates reflects the effectiveness of introducing the MenC vaccine.

Further research is necessary to better understand the decrease of WFS.