Recent changes in the epidemiology of invasive meningococcal disease in England

Introduction

Whilst rare in the UK, Invasive meningococcal disease (IMD) has relatively high mortality rates and can cause devastating sequelae including limb loss, cognitive impairments and hearing loss.Here we describe changes in the epidemiology of invasive meningococcal strains in England over the past 15 years.

Methods

The UK Health Security Agency’s Meningococcal Reference Unit performs laboratory confirmation and strain characterisation on meningococcal disease cases in England and Wales. Approximately half of cases involve submission of a clinical isolate and subsequent serogrouping, serotyping and whole genome sequence analysis. The remaining cases are confirmed and genogrouped from submitted clinical samples (e.g. blood and CSF) using a Taqman PCR assay targeting the ctrA and siaD capsular meningococcal genes.

Results

Total cases of group B IMD declined gradually from 2007 to 2019. This was partially due to the introduction of a group B vaccine into the UK infant immunisation programme in 2015, however, group B rates were declining prior to vaccine introduction. A drastic increase in group W disease was observed in England between 2010 and 2015 due to the spread of a hyper-invasive group W clonal complex 11 strain in the UK and elsewhere globally. Introduction of an MenACWY conjugate vaccine for adolescents served to reduce group W cases (and those of other serogroups) in the vaccinated population and other age groups through indirect herd protection.

In March 2020, the UK government introduced strict societal restrictions to curb the spread of SARS-CoV-2. This led to sharp reduction in IMD cases to historic low due to an interruption in transmission. From September 2021, after remaining COVID-19 restrictions had been lifted, group B IMD cases in 15-24 age group (particularly university students) have increased sharply and now exceed pre-pandemic levels.

Conclusions

IMD rates remain low in most age groups following the COVID-19 lockdowns, however, the recent sharp increase in group B cases among adolescents is a public health concern.