Hello, fever blisters is caused by virus herpes simplex type 1, it's different from varicella- zoster virus that causes chicken pox. If you've been struggling with fever blisters, it may indicate that your immune is getting weaker as you age. In this case, it's a reasonable choice to get a vaccine. The chicken pox vaccine is on live virus so there's a very small risk that people get chicken pox after getting the vaccine shot. But the case is rare cause the virus in the vaccine is weakened.