Summary

A medRxiv preprint finds that Ethiopia’s current meningococcal surveillance cannot determine whether protection from the MenAfriVac campaign is waning or which non-A serogroups are circulating. An indirect model estimates population protection fell from 85% in 2015 to 24% in 2024.

A new situational analysis says Ethiopia’s available national data cannot answer two important questions after its MenAfriVac campaign: whether protection against serogroup A meningococcal disease has declined enough for epidemics to return, and whether other meningococcal serogroups are circulating in the country.

The medRxiv preprint combines a review of historical records, secondary analysis of post-2015 surveillance data, modelling of population immunity and an assessment of the policy environment. The authors say the evidence base is too sparse for confident vaccine-policy decisions and propose rebuilding meningococcal surveillance as a tiered national system.

Contents

Why the post-campaign picture is difficult to assess

Ethiopia introduced MenAfriVac between 2013 and 2015 to control epidemics caused by meningococcal serogroup A, a defined group of meningococcal bacteria. The analysis reports that no MenA epidemics have been reported in Ethiopia since the campaign.

That absence of reported epidemics does not provide a complete picture of current population immunity or the serogroups present in the country. National disease notification currently depends on sentinel surveillance at three hospitals. None is located in the western regions identified as having epidemic risk, and none has a defined catchment population from which disease rates could be calculated.

Cases are rarely confirmed in laboratories, are almost never assigned to a serogroup, and are not reported promptly. Serogrouping is important because it identifies the bacterial group responsible for an infection and helps determine whether observed disease is related to the group targeted by a vaccine or to another group.

The authors also describe primary carriage and serosurvey studies as limited. Their varied populations, sampling methods and laboratory assays make it difficult to generalise their findings to Ethiopia’s population as a whole.

A model points to declining population protection

Because direct national measurements are insufficient, the analysis uses campaign coverage and regional waning models to estimate population protection. This indirect estimate fell from 85% in 2015 to 24% in 2024 and is projected to reach 11% by 2030 without intervention.

These percentages are model-based estimates rather than direct measurements from a single nationwide immunity survey. They are intended to indicate the scale of a possible protection gap while better surveillance data are developed.

The paper also describes a policy consequence of the limited evidence. The current E-NITAG prioritisation exercise relies on the sparse available data, excludes MenAfriVac from its candidate list and does not incorporate costing or serogroup-coverage data. Those omissions leave the assessment without several inputs needed to compare vaccine strategies and their expected reach.

The proposed surveillance system

The authors recommend a tiered surveillance structure. Primary healthcare facilities would identify suspected clinical cases. Regional and zonal hospitals would conduct confirmatory testing, while representative tertiary hospitals would perform serogrouping and genomic characterisation with support from a national laboratory system.

This arrangement would connect early case detection with increasingly detailed laboratory investigation. Over time, longitudinal data could show whether MenA disease is returning, identify non-A serogroups that may be causing disease, and provide a stronger basis for vaccine policy.

Until that system produces sufficient information, the authors recommend supplementary carriage and seroepidemiological studies. Carriage studies look for people carrying meningococci, while seroepidemiology examines population-level immune responses. Together, these approaches could help assess circulating serogroups and immunity alongside routine disease surveillance.

The work is a preprint based on records, secondary data, modelling and policy analysis rather than a clinical trial or an enrolled patient cohort. Its central contribution is identifying a surveillance and evidence gap: Ethiopia has had no reported MenA epidemics since MenAfriVac, but current national systems cannot reliably determine how durable protection is or which meningococcal groups are circulating.

Sources