Meningococci are bacteria which occur widely in healthy humans as part of the body’s natural ecosystem or ‘microbiota’. However, these bacteria are highly diverse, and some variants are more likely than others to cause the life-threatening diseases septicaemia or meningitis.
Children up to five years old, particularly infants, are at highest risk of meningococcal disease. The first national infant immunisation programme for the meningococcal vaccine ‘Bexsero’ targeting group B meningococci was launched in the UK in 2015. Research in the Department of Biology, in collaboration with Public Health Scotland and the Scottish Meningococcal Reference Laboratory, Glasgow, has assessed its impact using whole genome sequencing in real time.
Professor Andrew Smith (University of Glasgow), Head of the Scottish NHS Meningococcal Reference Laboratory, said:
This study represents a good example of integrated teamwork between University of Oxford, Public Health Scotland, the reference laboratory and the free to use PubMLST Public Database, based on the Meningitis Research Foundation Genome Library that allows our work to be repeated globally.
Detailed analysis of meningococci has historically been time and resource intensive, hindering real-time investigation of vaccine effectiveness – a key part of any vaccine implementation programme. More recently, molecular sequencing has become available, enabling precise and detailed characterisation of disease-causing variants across the whole population. The newly published study focused on tracking the bacteria causing post vaccination meningococcal disease in Scotland, where vaccine uptake was high at 95.4% uptake for the primary course and 93.5% uptake for the booster dose.
The results revealed that fully vaccinated children experienced no cases of disease caused by variants predicted to be covered by the vaccine – demonstrating the effectiveness of the vaccine. An incomplete schedule of doses provided poorer protection to infants, which was further reflected in those who didn’t receive any doses of the vaccine. Additionally, a lasting protective effect of the booster dose was seen in 3- and 4-year-old children who were fully vaccinated according to schedule. Where meningococcal disease was seen in fully vaccinated children, the genetic analyses showed that these were exclusively caused by meningococcal variants not predicted to be covered by the vaccine.
Professor Martin Maiden (Department of Biology) said:
Our findings give strong evidence of the efficacy of this vaccine, particularly when the schedule is fully completed. This should support public health and general practitioners in promoting vaccination according to schedule.
Childhood vaccinations can be delayed for many reasons, including illness, appointment delays, concern over side effects, and vaccine hesitancy or refusal. Refocusing efforts on positive and sustained messaging to carers and encouraging proactive identification and contact of unvaccinated children would help to prevent such cases.
Future work to characterise meningococcal variants and their interaction with vaccine-induced immunity will be of great benefit. This will allow public health authorities in diverse global regions to assess potential vaccine impact in their populations, permitting improved cost-effectiveness estimates and improving evidence-based vaccine policy decisions.
To read more about this research, published in mBio, visit: https://doi.org/10.1128/mbio.00499-23