Streptococcus pneumoniae, commonly called pneumococcus, can cause a wide range of diseases in children from mild ear infections to deadly pneumonia or meningitis. Vaccination is currently the single best way to protect children. Nutrition, especially the amount of vitamin A, may play a role in how well your body responds to infection or a vaccine. We call this an immune response. This research will look to see if children who take a vitamin with their vaccine have a better immune response than children who do not take a vitamin with their vaccine. Primary Objective To evaluate the influence of vitamin A supplementation on Prevnar vaccine immunogenicity based on changes in antibody scores in a commercial ELISA at Day 21 (after a booster vaccine dose) compared to pre-vaccine values. Secondary Objectives * To evaluate the relationship between baseline vitamin levels and pneumococcal or hepatitis A vaccine antibody responses (based on in commercial ELISAs) at Days 0 and 21. * To evaluate the influence of vitamin A supplementation on hepatitis vaccine immunogenicity based on changes in antibody scores in a commercial ELISA at Day 21 compared to pre-vaccine values. * To evaluate relationships between total serum antibodies (based on individual IgM, IgG1, IgG2, IgG3, IgG4, and IgA scores in a Luminex assay) at Day 0 and changes between Days 0 and 21 with baseline (Day 0) vitamin levels in young children, and with vitamin A supplementation.