Meningococcal Vaccin. Meningococcal vaccine preteens and teens : mcv4 Meningococcal conjugate vaccine protects against some bacteria causing meningitis or bloodstream infection. Recommended for all preteens at age 11 or 12. Booster shot recommended for teens at age 16 through 18. Essential if they are about to move into a college dorm or military barracks.