Herd immunity, a process in which resistant individuals limit the spread of a pathogen among susceptible hosts has been extensively studied in eukaryotes. Even though bacteria have evolved multiple immune systems against their phage pathogens, herd immunity in bacteria remains unexplored. Here we experimentally demonstrate that herd immunity arises during phage epidemics in structured and unstr...

results overall hav seropositivity in nursing students (mean age 24, range 17 - 45 years) was 3%. compliance to preventive measures was not uniform (6% - 76%) and extremely low in some specific measures targeted to decrease the oral-fecal transmission. conclusions the high proportion of susceptible nursing students can contribute to an increase in the risk of nosocomial transmission, especially...

While the Latin phrases in vitro and in vivo are well understood in the medical literature, neither term accurately describes the science performed at the level of the population by epidemiologists and others. In particular, the effect of an exposure in a single organism can differ from those in a population, for reasons ranging from random error to herd immunity. We suggest that in populo (mea...

The recent threat of bioterrorism has fueled debate on smallpox vaccination policy for the United States. Certain policy proposals call for voluntary mass vaccination; however, if individuals decide whether to vaccinate according to self-interest, the level of herd immunity achieved may differ from what is best for the population as a whole. We present a synthesis of game theory and epidemic mo...