An OMV vaccine derived from a capsular group B meningococcus with constitutive FetA expression: preclinical evaluation of immunogenicity and toxicity by Norheim, G, Sanders, H, Mellesdal, J, Sundfør, I, Chan, H, Brehony, C, Vipond, C, Dold, C, Care, R, Saleem, M, Maiden, M, Derrick, J, Feavers, I, Pollard, A