Can you tell me in which decade do you think the vaccine for diptheria was introduced in england and wales?

Early 50's: The vaccine was first made available in the United States. That happened in 1945, and it almost immediately became routinely used in the US. Although I could not find an exact date, it looks like from cause of death in children tables that diphtheria deaths were quite epidemic yet in England & Wales until the late 1940's, so routine use probably started in the early 1950's in that region.