Original sentence: The African green monkey has been the focus of much scientific research since the 1950s, and its tissues are still used today to produce vaccines for polio and smallpox.This is done by infected living monkeys, letting the infection "incubate," killing the monkey, then harvesting the tissue
Edited sentence: The African green monkey has been the focus of much scientific research since the 1950s and its tissues are still used today to produce vaccines for polio and smallpox.This is done by infecting living monkeys, letting the infection "incubate," killing the monkey, then harvesting the tissue