"We are just waiting for the first cases of measles – or something else – because we are finding that the majority of children coming from the Central African Republic have never been vaccinated," Nagué says.
It said it was increasing operations to help more families with heating, children's clothes and a vaccination programme to protect up to a million children against measles and other diseases.
"My infant daughter went blind after contracting measles from an unvaccinated child, and yet there's no braille version of this wonderful book for me to give her someday to explain to her how awesome the disease that took her sight away is," wrote one user.
"Let's take her some carrot juice and melon to help her get strong and recover from the measles".
With a cover showing a rash-covered girl playing in the garden, Messenger's story sees Tina worrying about her friend Melanie, who is away from school with measles.
Last week he found himself at the centre of storm after drawing comparisons between the response to Ebola in west Africa and a measles outbreak in north America.
Related: Roald Dahl becomes sage of US measles outbreak Its title riffs on George's Marvellous Medicine by the author Roald Dahl, who himself extolled the virtues of vaccination, after his seven-year-old daughter Olivia died from measles encephalitis.
The measles outbreak has renewed a debate over the so-called anti-vaccination movement in which fears about potential side effects of vaccines, fueled by now-debunked research suggesting a link to autism, have led a small minority of parents to refuse to allow their children to be inoculated.
In round one of our Twit-interviews we spoke to the people behind the most followed accounts in Tanzania and Uganda, and a Nigerian satirist who recently found himself at the centre of a social media storm after he compared Ebola to the measles outbreak in North America.
But since the measles outbreak in California's Disneyland last month spread to more than 100 people, it has received more than 800 one-star reviews on Amazon.com as readers laid into the title.
The charity said across the 10 countries, less than half of the children seen in its consultations were properly immunised against tetanus, measles, mumps and rubella and more than half pregnant women had not had access to antenatal care until they were well into their second trimester.
