Roald Dahl is probably at the top of any book nerd's list of children's authors — and there's a reason his books are still so good at getting into the heads of imaginative children. The Llandaff, Cardiff native had four children, but one of Roald Dahl's daughters died when she was pretty young. Olivia was his eldest daughter with Patricia Neal and died in 1962 from measles when she was just 7 years old. It wasn't until 1986 that the famed writer spoke publicly about it, true to form, in a moving essay about her illness and how helpless he felt taking care of her. It's especially timely, even now, because of the current debate about vaccines and their effects.

In his essay, Dahl wrote of Olivia's final moments:

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 essay goes on to talk about how, in 1986, he wished that there had been something to do about Olivia's measles. In 1960, he wrote, there was no "reliable" vaccine, as he put it. So his daughter was susceptible to the virus.

Dahl eventually ended up dedicating James and the Giant Peach to Olivia while she was still alive, and The BFG to her after she had died. (When you watch the movie in these coming weeks, despite the reviews, eat some popcorn for Olivia.)

Dahl was very outspoken about measles and didn't mince words about the need to vaccinate children. He wrote in 1986 essay:

Here in Britain, because so many parents refuse, either out of obstinacy or ignorance or fear, to allow their children to be immunized, we still have a hundred thousand cases of measles every year. Out of those, more than 10,000 will suffer side effects of one kind or another. At least 10,000 will develop ear or chest infections. About 20 will die. ... So what on earth are you worrying about? It really is almost a crime to allow your child to go un-immunized.

Dahl's frustration is mirrored in the current discussion among parents about whether vaccines are necessary. Of course they are. In 2015, there were 189 outbreaks of the measles in the United States. In 2014, 667. Most of those cases, according to the Centers for Disease Control, were among unvaccinated communities. And it spreads.

When children aren't vaccinated, everyone suffers. Dahl's own experience should be taken seriously, even if his stories seem based in fantasy.