Constant administration of vaccine syringes is required to stall the parasite's maturation. Failure to inject results in immediate internal biological collapse.
The developer has released source code for some versions, often available via Itch.io or GitHub.
You can mod Endoparasitic or its sequel by using GDRE.tools to recover the project files and the Godot editor (version 4.x is often recommended for newer entries) to build new scenes or scripts.