Vaccines can be used to protect against viruses and bacteria. But bacteria can sometimes be harder to fight. I’m Mindy Cook with your latest health news. Serotypes are different strains of bacteria that can make people sick. This means vaccines usually must be designed to address as many of the different serotypes for bacterial illnesses as possible. According to a recent study, the current vaccine for invasive pneumococcal disease protects against 13 strains of the bacteria, but children are still getting sick from other strains. Discuss the recommended immunization schedule with your child’s pediatrician.