Meningitis vaccine programme providing herd immunity across all age groups

The research demonstrates the impact of the vaccine in generating herd protection, also called herd immunity, that enables protection for all age groups. 

In the study, which is published in Clinical Microbiology and Infection, the researchers took throat swabs and assessed the prevalence of meningitis-causing bacteria before and after the introduction of the vaccination programme, using two cross-sectional studies conducted almost four years apart. They found the vaccine substantially reduced carriage of the W and Y meningococcal groups, and sustained low levels of the C group. 

In 2015, responding to rising rates of meningitis cases driven by the W and Y strains from 2009 onwards, the UK replaced a vaccine targeting only the C group (introduced in 1999) with quadrivalent MenACWY vaccines. To maximise the likelihood of herd immunity, teenagers aged 14 to 19, where transmission of the meningococcal bacteria is known to be highest, were prioritised for vaccination. 

Professor Martin Maiden, Professor of Molecular Epidemiology and one of the lead authors, said:

"We have been systematically investigating meningococcal vaccination and its effects on carriage in Oxford since 1999.  These studies have been crucial in enabling the most effective use of meningococcal vaccines around the world."

The findings align with data from UK has showing that the incidence of MenW disease has fallen in all age groups since the teenage MenACWY vaccine campaign, not just in teenagers themselves. Taken together, thisese data provides strong evidence for the need to target age groups with high rates of meningococcal transmission, to make most effective use of these vaccines, and not necessarily immunising other age groups at high risk e.g. infants. 

One of the lead authors, Matthew Snape, Professor in Paediatrics and Vaccinology at the Oxford Vaccine Group said: 

"Immunising teenagers rather than infants means we get more benefit out of each dose given. These two studies therefore provide invaluable data to help us use these vaccines effectively, both in the UK and internationally."

The work by the Maiden lab has previously characterised meningitis variants that has informed meningitis vaccine policies around the world. 

Professor Martin Maiden concludes: 

"In combination with our work with colleagues at Public Health England (now HSA) that characterized the MenW epidemic variant at the genomic level, this work helped to interrupt an epidemic that would likely have affected thousands of individuals. This demonstrates the importance of long-term studies that permit the anticipation of epidemics and pandemics and enables them to be curtailed before they impact the population too severely."

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