A letter Roald Dahl, the late British novelist known for titles such as Matilda and The BFG, published in 1962 in favor of the measles virus vaccination is making its way around the Internet in light of the recent outbreak, the country’s worst case in 20 years.

Dahl is an advocate for this particular vaccine because his daughter, Olivia, who was 7, died of the virus. At the time of her death, there was no vaccine available; the first wasn’t licensed in the U.S. until the following year, reported The Telegraph. And while the letter touches on his final days with Olivia, it ends with a plea for parents to get their child vaccinated, to do what he was unable to do for his daughter.

Here's an excerpt:

Olivia, my eldest daughter, caught measles when she was seven years old. As the illness took its usual course I can remember reading to her often in bed and not feeling particularly alarmed about it. Then one morning, when she was well on the road to recovery, I was sitting on her bed showing her how to fashion little animals out of coloured pipe-cleaners, and when it came to her turn to make one herself, I noticed that her fingers and her mind were not working together and she couldn’t do anything.

“Are you feeling all right?” I asked her.

“I feel all sleepy,” she said.

In an hour, she was unconscious. In twelve hours she was dead.

The measles had turned into a terrible thing called measles encephalitis and there was nothing the doctors could do to save her. That was twenty-four years ago in 1962, but even now, if a child with measles happens to develop the same deadly reaction from measles as Olivia did, there would still be nothing the doctors could do to help her.

On the other hand, there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. I was unable to do that for Olivia in 1962 because in those days a reliable measles vaccine had not been discovered. Today a good and safe vaccine is available to every family and all you have to do is to ask your doctor to administer it.”

Click over to roalddahl.com for the rest of the novelist's heartbreaking plea.