Concept of Cross-Protection and Herd Immunity 

Basic Vaccine Immunology 



08 November 2023 

14:30 – 14:50H 



Jin Oh Kim  

MSD AP Region 



Herd protection is usually defined as Immunization of large portions of the population to protect the unvaccinated, immunocompromised, and immunologically naive by reducing the number of susceptible hosts to a level less than the threshold needed for transmission”.  

Key topics will be 1. Definition of herd immunity and implications in community protection; 2. Examples of herd immunity in some selected vaccines; 3. Key parameters in herd immunity and threshold in various vaccines; 4. Vaccine hesitancy, COVID-19 Impact and measles outbreaks; 5. Herd Immunity and COVID-19 

Cross-protection is defined as clinically significant protection against infection/disease due to an immune response elicited against a related organism. 

Key topics will be 1. Cross-reactivity and cross-protection; 2. Cross protections in various vaccines; 3. Example of cross-protection approach in developing universal flu vaccine; 4. Cross-protection and COVID-19