I would like to plot vertical confidence interval graph instead of horizontal confidence intervals graph.

Something like this:

from

To have the bars appear on the whiskers, you may need to draw over the default error bars as the width have been hard-coded.

p coord_fixed()   
  theme(axis.text.x = element_text(angle = 90))   
  geom_errorbar(
    aes_string(ymin = "conf.low", ymax = "conf.high"),
    width = 0.25
  )