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 leverage herd immunity effects, the vaccination programme enrolled teenagers aged 14 to 19, where transmission of the meningococcal bacteria is known to be highest.