A woman who became the first person to die of the measles in the U.S. in 12 years had been vaccinated against the disease, it has been revealed.

Health officials said she had the injection as a child but succumbed because she had a compromised immune system.

Dr. Jeanette Stehr-Green, the Clallam County health officer, told KOMO-TV the woman had been vaccinated as a child, but because she had other health problems and was taking medications that interfered with her response to an infection 'she was not protected.'

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The return: An autopsy has revealed that a Washington State woman died of measles in the spring - marking the first measles death in the U.S. since 2003. Above, a stock image of a measles vaccination

The female patient, who passed away in the spring, lacked some of the measles' common symptoms, such as a rash, so the infection was not discovered until an autopsy, Washington State Department of Health spokesman Donn Moyer said.

This is the 11th case of measles in Washington - and the sixth in Clallam County - this year, Moyer said.

Measles is highly contagious and spreads when an infected person breathes, coughs or sneezes. However, dying from it is extremely rare, Moyer said.

Officials didn't say whether the woman was vaccinated, but they did note she had a compromised immune system. They withheld her age to protect her identity but said she was not elderly.

The woman was hospitalized for several health conditions in the spring at a facility in Clallam County, which covers the northern part of the Olympic Peninsula. She was there at the same time as a person who later developed a rash and was contagious for measles, Moyer said. That's when the woman most likely was exposed.

She was on medications that contributed to her weakened immune system, he said.

After being treated in Clallam County, the woman was moved to the University of Washington Medical Center in Seattle, where she died. An autopsy concluded the cause of death was pneumonia due to measles.

'This tragic situation illustrates the importance of immunizing as many people as possible to provide a high level of community protection against measles,' Moyer said. 'People with compromised immune systems cannot be vaccinated against measles. Even when vaccinated, they may not have a good immune response when exposed to disease; they may be especially vulnerable to disease outbreaks.'

The last active case of measles in Washington was reported in late April.