The proposed study is a single centre, open−label, randomised, controlled study in 150 healthy adults aged 18−70 years. The participants will be given either 2 injections of the meningococcal protein−polysaccharide conjugate vaccine one month apart, or one injection of the meningococcal plain polysaccharide vaccine followed one month later with an injection of the meningococcal conjugate vaccine. Blood samples will be collected before immunisation and at several time points following immunisations to evaluate the level of meningococcal specific antibody induced by two different vaccination regimes. The data derived from the study will be relevant in determining which of these vaccines should be used in preference in travellers who are receiving immunisation against meningococcal disease before travelling to high risk areas. Additionally, a number of scientific questions regarding the nature of the immune response to the two vaccines (specifically looking at the white blood cells responsible for producing antibodies, known as B cells) and the role of genetic variations in influencing the vaccine recipient's immune response will be addressed in the study.