Title: Meningitis Vaccine Clinical Trial in Infants Description: A vaccine works by helping your immune system to fight off germs. Bexsero is a vaccine that can help protect against a germ called group B Meningococcus. This germ can cause several serious diseases, including meningitis. Meningitis affects the brain and spinal cord. Meningitis can happen to anyone but is more common in teenagers, and young children (including babies). In European countries, the vaccine is approved for people aged 2 months and older. In the US, Bexsero is approved by the Food and Drug Administration (FDA) for people from the age of 10 years to 25 years. This study will be done in children between 42 and 84 days of age (6 through 12 weeks) at the time of the first study vaccination.