Are there any real baby outcome studies comparing delayed vs on-time schedules?

Short answer: no. What exists is antibody comparisons between schedules, plus two timing studies with real outcomes that cut in opposite directions.

The retrieved trials comparing schedules (2-4-6 vs 3-5, 1+1 vs 2+1, three-dose vs four-dose) all measured antibody levels, not whether babies got sick or developed normally [1][2]. A booster dose largely equalized antibody responses across schedules in Dutch, UK, and Nepalese infants [2]. That is a lab readout. It cannot tell you whether delaying changes real health outcomes, and none of these trials measured neurodevelopment, infections, or allergy over time [1][2].

Two studies did use real outcomes, and they point both ways. In very preterm NICU babies, vaccination at 70 days or younger was linked to major breathing and heart-rate events in 9 of 27, versus none in those vaccinated later [3]. But for rotavirus, the opposite: delayed first doses in older infants tracked with more intussusception cases, a bowel-blockage injury [5]. So "delay is safer" is not a general truth; it is vaccine- and baby-specific.

What this retrieval cannot see: any trial in healthy term infants comparing a delayed schedule to the on-time schedule on clinical outcomes like infection, hospitalization, or development. Such studies may exist outside this search; none surfaced here. The BCG birth-versus-delayed trial measured immune markers only, which waned to near-equal by one year [4].

My call: the evidence is not clear. Schedule comparisons exist, but they stop at antibody levels; the only hard-outcome timing data retrieved involves preterm infants and rotavirus, not the healthy-term delay question you are asking. Confidence: low.