Ministry director Leausa Dr Take Naseri said once ministry staff realised human error was behind the vaccine-related deaths of two infants in 2018, the health system had to overhaul its processes.
The two one-year-old babies died after receiving doses of the MMR vaccine, which were incorrectly mixed with an expired anaesthetic.
The deaths prompted Samoa to suspend all vaccination for three months and damaged public trust in vaccines across the region.
Dr Naseri said everything had to be reviewed in Samoa, including how medication cupboards were stocked, and staffing accounted for nursing drug checks, with a focus on improving safety.
"This entails a lot of training. Not only a classroom approach...Hands on training also, and how they manage things so that we'll avoid all these mistakes, and be proactively involved in protecting and preventing what may happen again."
Dr Naseri said the training and procedures had already been in place but people became complacent.
Samoa's government declared a measles epidemic in mid-October.
Two young children and a 37-year-old man recently died in Samoa, after clinical signs indicated they had measles.
Meanwhile, new global research has revealed the virus is even more dangerous than first realised because it destroys immunity to other diseases.
The findings from studies by Britain's Wellcome Sanger Institute, Cambridge University and the Howard Hughes Medical Institute in the US, help to explain why children often catch other infectious diseases after having measles.