Abstract
Invasive meningococcal disease causes significant morbidity and mortality worldwide, with serogroup B being one of the predominant serogroups in Australia for many years. The South Australian (SA) State Government recently funded the introduction of a 4CMenB vaccination program for infants, children and adolescents. In addition to protecting against invasive meningococcal disease, emerging evidence suggests the 4CMenB vaccine may also be effective against gonorrhoea due to genetic similarities between Neisseria meningitidis and Neisseria gonorrhoeae. The proposed project aims to evaluate the effectiveness of the SA 4CMenB vaccination program against invasive meningococcal disease and gonorrhoea through a combination of observational studies using routine surveillance and research data. The main methodological approaches involve an interrupted time series regression model, screening, and case-control analyses with different sets of controls to estimate vaccine impact and effectiveness. These analyses are designed to minimize potential biases inherent in all observational studies and to provide critical data on the effectiveness of the 4CMenB vaccine against two diseases of major global public health concern.