What are “immunity debt” and “immunity gap”?

On November 23, 2023, the World Health Organization's official website published an article titled "Surge in respiratory diseases among children in northern China", which attracted the world's attention to this current concern. On November 24, Maria Van Kerkhove, executive director of the World Health Organization's Epidemic Preparedness Department, said in an interview with STAT that the main reason for the surge in respiratory infections among children in China is the immunity gap related to the new crown epidemic.

What is the “immunity gap”?

"Immune gap" and "immune debt" are almost the same concept, referring to the increase in the number of people who are not immune to pathogens due to a long period of lack of contact with pathogenic microorganisms. "Immune gap" is a common academic term, while "immune debt" is more commonly used in the media. In addition, the former is more neutral, while the latter is somewhat derogatory and sometimes even misleading.

In order to avoid the misunderstanding that the term "immunity debt" may cause, the term "immunity gap" is used uniformly in this article. Specifically, the "immunity gap" related to the COVID-19 pandemic refers to the fact that due to strict epidemic prevention measures, people lack the opportunity to come into contact with some pathogens (such as pathogens that cause respiratory infections), which increases the proportion of people in the population who are not immune to these pathogens. When epidemic prevention measures are lifted, diseases caused by these pathogens may surge.

Specifically, the "immunity gap" related to the COVID-19 pandemic refers to the fact that due to strict epidemic prevention measures, people lack the opportunity to come into contact with certain pathogens (such as pathogens that cause respiratory infections), which leads to an increase in the proportion of people who lack immunity to these pathogens. The "immunity gap" is a normal phenomenon that has little impact on individual immunity and mainly affects the group level, such as the surge in respiratory infections in the post-COVID era.