Where do vaccines to break the chain of infection? a. at the susceptible host b. at the portal of exit c. at the means of transmission d. at the reservoir

A. At the susceptible host

Explanation: For a person to become infected with a pathogen, he or she must be a susceptible host. A susceptible host is someone who is able to contract the pathogen. Vaccines can help break this link in the chain of infection, therefore making a person not susceptible. Susceptibility of a person depends on several factors:

* The number and species of pathogen

* The duration of exposure to the pathogen

* The host’s overall general physical condition

* The host’s psychological health status

* The host’s occupational or lifestyle environment

* The presence of underlying diseases or conditions in the host

* Age of the host... PF