Premature infants are at a higher risk for invasive disease with Streptococcus pneumoniae. The heptavalent pneumococcal-CRM197 conjugate vaccine (PCV-7) effectively prevents invasive pneumococcal disease in full-term infants, but was been incompletely studied in premature infants. The American Academy of Pediatrics (AAP) recommends that "prematurely born infants, including infants of low birth weight, should be immunized at the usual chronological age in most cases", but cautions that "some studies suggest a reduced immune response in very low-birth-weight infants (<1500 g)."