© 2018 American Physical Society. We thoroughly study the photo-disintegration of He4 on the cosmic microwave background using the most recent cross-section data from both the inclusive measurement observing the analog of the giant dipole resonance in He4 through the charge-exchange spin-flip He4 (Li7,Be7) reaction and from measurements of exclusive two-body and three-body processes: He4(γ,p) H3, He4(γ,n) He3, and He4(γ,pn) H2. We show that the present-day (redshift z=0) mean-free path of ultrarelativistic (Lorentz factor ∼1010) helium nuclei increases by more that 15% with respect to previous estimates adopted as benchmarks for Monte Carlo simulation codes of ultrahigh-energy cosmic ray propagation. This implies that the physical survival probability of He4 nuclei would be larger than predicted by existing event generators. For example, for E∼1010.8 GeV and a propagation distance of 3.5 Mpc, the He4 intensity would be 35% larger than the output of the CRPropa 3 program and 42% larger than the output of the SimProp v2r4 program. We provide new parametrizations for the two-body and three-body photo-disintegration cross sections of He4, He3, tritium, and deuterium.