To evaluate the effects of influenza vaccination with or without heptavalent pneumococcal conjugate vaccination on respiratory tract infections (RTIs) in children. This was a randomized, double-blind, placebo-controlled trial comprising 579 children age 18 to 72 months with a previous history of physician-diagnosed RTI, recruited between 2003 and 2005. The children were assigned to 2 doses of parenteral inactivated trivalent subunit influenza plus heptavalent pneumococcal conjugate vaccination (TIV+PCV7), influenza plus placebo vaccination (TIV+plac), or control hepatitis B virus vaccination plus placebo (HBV+plac). Main outcome measures were febrile RTI and related polymerase chain reaction (PCR)-confirmed influenza, primary care visits, antibiotic prescriptions, and acute otitis media (AOM) episodes. During influenza seasons, febrile RTI were reduced by 24% (95% confidence interval [CI] = 1% to 42%) in the TIV+PCV7 group and by 13% (95% CI = -12% to 32%) in the TIV+plac group compared with the control group. The occurrence of PCR-confirmed influenza was reduced by 52% (95% CI = 7% to 75%) in the TIV+PCV7 group and by 51% (95% CI = 3% to 75%) in the TIV+plac group. Episodes of AOM were reduced by 57% (95% CI = 6% to 80%) in the TIV+PCV7 group and by 71% (95% CI = 30% to 88%) in the TIV+plac group. Outside of the influenza seasons, no significant effects of vaccinations were demonstrated on the studied outcomes. During influenza seasons, influenza vaccination with or without pneumococcal conjugate vaccination substantially reduced cases of confirmed influenza and AOM episodes.