Which infection is most likely to confer life-long immunity after infection?

The infection that is most likely to confer life-long immunity after infection is rubella. After a person has contracted rubella, their immune system typically develops a strong and lasting response against the virus. This is similar to the way the body responds to a vaccination, allowing individuals to have protection against future infections.

Measles and chickenpox also provide long-lasting immunity, but rubella is often highlighted specifically for its robust, life-long immunity post-infection. Influenza, on the other hand, tends to change frequently due to antigenic drift and shift, meaning that immunity from a previous infection may not protect against different strains encountered in the future.

This understanding of rubella's immunity is critical for public health, especially in populations vulnerable to congenital rubella syndrome.