Isso parece ser Needle (1950), de Hal Clement.
A partir da descrição do Wiki, vemos muitos dos elementos descritos.
Um simbionte alienígena, na verdade não uma ameba, mas uma espécie de aparência próxima (apenas muito maior) e a presença de um fugitivo.The Hunter, an alien lifeform (when not inside another being, resembling a four-pound green jellyfish) with the ability to live in symbiosis with and within another creature, is in hot pursuit of another of his kind. Both crash their ships into Earth, in the Pacific Ocean, and both survive the crashes.
Adolescente
The Hunter makes its way to shore (its erstwhile host having been killed in the crash) and takes up residence in the nearest human being it can find (as it turns out, fifteen-year-old Robert Kinnaird) without letting the human being know.
Fator de cura (depois que o alienígena se revelou para o host):
Upon arrival, the two begin to seek out their quarry. Bob is injured by an accident. The Hunter is able to hold the wound together, but he can't stop Bob from limping, and Bob is sent to the island doctor.
Mais sobre o fator de cura, e o fugitivo sendo o pai de Bob:
Não consigo encontrar nenhuma citação para o pai estar envolvido em um equivalente da NASA ou de foguetes em geral, e minha memória do livro é muito antiga para fornecer pessoalmente a confirmação, mas parece muito perto de tudo.The Hunter is able to solve the riddle by observing the behavior of the island people. Bob's father, known for his attention to detail and safety, has been taking amazing risks. He is at least unconsciously aware that an accident will have no ill consequences. The quarry resides within him. The Hunter confirms this, and Bob and the alien have a new puzzle—how to get the alien out of Mr. Kinnaird's body without harming the man?