The film partnered with Claire's Place Foundation; A charity to emotionally and financially support families struggling with Cystic Fibrosis. Both actors and director worked closely to assure accuracy with the depiction of cystic fibrosis in the film.
Late Claire Wineland worked closely with lead actors Haley and Cole on perfecting the roles of cystic fibrosis patients. Claire died in September 2018 after experiencing a stroke right after a successful lungs transplant.
The trivia item below may give away important plot points.
The movie ends with Will leaving Stella after she gets her new lungs so that she may be safe from his germs. However in the book Will and Stella run into each other in the airport months laters. While Stella is looking much healthier, Will is still just as sick as before. The book has more of an open ending as to what happens between them.