Antonyms for the phrase "more transmissible," which refers to the ability of a disease to spread quickly between people, include "less contagious," "less infectious," "less communicable," and "less viral. These antonyms suggest a lower risk of transmission, which is of great importance in controlling the spread of infectious diseases. Conversely, if a disease is described as more transmissible, it means that it has a greater ability to infect others, which can result in exponential growth of the disease. Therefore, it is crucial to take preventative measures, such as social distancing, wearing masks, and vaccination, to reduce the risk of transmission and prevent the further spread of diseases.