The opposite of becoming infected with is to become immunized against. Immunization is the process of rendering a person or animal immune or resistant to a disease by administering a vaccine or drugs. Another antonym for becoming infected with is to remain healthy or uninfected. This could be achieved by taking precautions such as washing one's hands regularly, maintaining hygiene, avoiding contact with sick people, or staying away from disease outbreaks. Additionally, some people are naturally resistant to certain infections due to their genetics or previous exposure to the disease. In conclusion, becoming immunized or remaining healthy are the antonyms for the phrase "become infected with.