Final answer:
Nursing homes must offer immunization against influenza or the flu to all residents from Oct 1 to March 31 of each year.
Step-by-step explanation:
The disease that nursing homes must offer immunization against to all residents from Oct 1 to March 31 of each year is influenza or the flu. The Centers for Disease Control and Prevention (CDC) strongly recommends a yearly flu vaccine for everyone who is at least 6 months of age, especially for individuals who are at high risk of developing serious complications if they get sick with the flu. This includes people with certain medical conditions, pregnant women, young children, and older adults.