1. the process of making a person or animal immune to a disease, typically by vaccination
Usage: British English spelling; American English uses 'immunization'; often used in medical and public health contexts
2. protection against a disease or harmful influence
Usage: figurative use

Examples

• The immunisation programme has helped eliminate measles in many countries.
• Children receive immunisation against polio during their first year of life.
• Mass immunisation campaigns are essential for controlling infectious diseases.
• The doctor recommended immunisation before traveling to tropical regions.
• Immunisation records must be kept up to date for school enrollment.
• Public health officials are promoting immunisation to prevent outbreaks.