immunity gap

Meanings

1. The time period during which a young mammal no longer receives effective immunity to diseases from antibodies in its mother's milk but its own immune system is not fully developed.
2. The time period between when an individual's or a population's immunity to a virus has waned (due to normal decrease in immune response over time or to the development of a new strain of the virus) and before a new vaccine can be given to boost immunity.
3. Used other than figuratively or idiomatically: see immunity, gap.