Final answer:
When an individual's immune system prevents transmission, it prevents the spread of disease. Vaccines contribute significantly to this protection by inducing immunity, which can lead to herd immunity within a population. Good hygiene practices also play a critical role in preventing disease transmission.
Step-by-step explanation:
When an individual's immune system prevents transmission, it prevents the spread of disease. This occurs because a functioning immune system can successfully fight off pathogens, such as bacteria, viruses, or fungi, before they can spread or cause illness. Immunizations play a key role in this process, as vaccines inhibit the virus by blocking the action of key viral proteins and by controlling and reducing symptoms. Consequently, a high level of vaccination in a population provides herd immunity, which protects those who cannot be vaccinated. It's essential for individuals to also practice good hygiene, such as frequent handwashing, to further prevent the spread of infectious diseases.