Public Health Wales has reported that the number of measles cases has risen to 886, as children have gone back to school after Easter. 25-year-old Gareth Williams died during the epidemic, it has not been confirmed whether measles was the cause.
Health Secretary Jeremy Hunt said that the "myth" surround the MMR jab must be "slayed", after health officials reported that the number of measles cases had risen to 886.
Shamed doctor Andrew Wakefield was struck off the medical register for his discredited research which claimed to find a link between autism and the MMR vaccine.
Speaking to the Health Select Committee, Mr Hunt said: "We certainly must not think of this as something that is just happening in Wales.
"[There] is still that critical 11 to 15-year-old age group that may not have been vaccinated because they were toddlers at precisely the time when the MMR scare was so appallingly whipped up.
"I want to reassure you, we are taking this extremely seriously inside the Department of Health."
A man who died in from a suspected case of measles in Wales was infected with the disease at the time of his death, health officials said.
A mother convinced the MMR vaccine led to her son's autism has not immunised her daughter, despite the link being disproved.