  Five fast radio bursts (FRBs), including three apparently non-repeating ones
FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB
180916.J0158+65, have already been localized so far. We apply a method
developed recently by us (Li et al. 2019) to these five localized FRBs to give
a cosmology-insensitive estimate of the fraction of baryon mass in the IGM,
$f_{\rm IGM}$. Using the measured dispersion measure (DM) and luminosity
distance $d_{\rm L}$ data (inferred from the FRB redshifts and $d_{\rm L}$ of
type Ia supernovae at the same redshifts) of the five FRBs, we constrain the
local $f_{\rm IGM} = 0.84^{+0.16}_{-0.22}$ with no evidence of redshift
dependence. This cosmology-insensitive estimate of $f_{\rm IGM}$ from FRB
observations is in excellent agreement with previous constraints using other
probes. Moreover, using the three apparently non-repeating FRBs only we get a
little looser but consistent result $f_{\rm IGM} = 0.74^{+0.24}_{-0.18}$. In
these two cases, reasonable estimations for the host galaxy DM contribution
(${\rm DM_{host}}$) can be achieved by modelling it as a function of star
formation rate. The constraints on both $f_{\rm IGM}$ and ${\rm DM_{host}}$ are
expected to be significantly improved with the rapid progress in localizing
FRBs.
