immunité collective naturelle

CONT: Dans les pays riches, les progrès de l'hygiène font reculer les infections à transmission féco-orale, mais diminuent l'immunité collective naturelle contre les agents [causant les hépatites virales].

CONT: ... natural herd immunity, achieved through infection rather than vaccination, can be challenging due to high rate of serious illness and death, with health systems overwhelmed well beyond their surge capacity, even in high-income countries.