elekos - actually the 6-in-1 can take at 1.5 mths already. The doc gave me a leaflet which shows the schedule for the different type of vaccinations, for 6 in 1, can take at 1.5, 3 or 5 mths or 2,4,6 mths. We chose to do the 2,4,6 mths schedule. Since we did the 6 in 1, then no need to do the Hep B one separately.