Month = seq(1,12)
Median_Peak_Duration = c(6,5,4,3,1,2,2,3,4,4,5,5.5)
PeakyMonth = ifelse(Median_Peak_Duration > 3, 'Non-Peaky', 'Peaky')
testDat = data.frame(Month, Median_Peak_Duration,PeakyMonth)

testDat %>%
ggvis(x = ~Month, y = ~Median_Peak_Duration, fill = ~PeakyMonth) %>%
layer_bars(width = .8) %>%
# Annotation
layer_lines(x = ~Month, y = 3, strokeDash := 6, strokeWidth := 3) %>%
layer_text(x = 6, y = 4.5, text:= "Some more Text",
  fontSize := 12, align := "center", baseline := "top", fill := "black") %>%
layer_text(x = 6, y = 3, text:= "Some Text",
  fontSize := 12, align := "center", baseline := "top", fill := "black")

testDat %>%
ggvis(x = ~Month, y = ~Median_Peak_Duration, fill = ~PeakyMonth) %>%
layer_bars(width = .8) %>%
# Annotation
layer_lines(x = ~Month, y = 3, strokeDash := 6, strokeWidth := 3) %>%
layer_text(x = 6, y = 4.5, text:= "Some more Text",
  fontSize := 12, align := "center", baseline := "top", fill := "black")