A randomized trial in infants less than 32 weeks gestation at birth compared changes in levels of C-reactive protein, prostaglanding E2 (PGE2) and the frequency of cardio-respiratory events after the infants received the two-month vaccinations. The intervention group received ibuprofen and controls received placebo. Infants had an elevation in CRP levels following immunization. PGE2 levels did not change. They also had an increase in cardiorespiratory events, which was greater in infants receiving placebo than those receiving ibuprofen. Ibuprofen did not blunt the increase in CRP levels.