Can vaccination be used to control outbreaks of varicella?
Varicella outbreaks in closed settings (e.g. child care centers, schools, institutions) tend to be protracted and go through several generations of infection before coming to an end in the absence of an intervention. School outbreaks have been documented to last for 3-6 months. Varicella vaccine has been used successfully by state and local health departments and by the military for outbreak prevention and control. Although the vaccine works by preventing illness or modifying the severity of illness in those vaccinated within 3 days and possibly up to 5 days after exposure, most of the benefit of vaccinating all susceptible individuals in an outbreak in a closed setting derives from vaccinating persons before exposure, since few individuals are actually infected in the first generation. For this reason, although it is desirable to intervene as early in an outbreak as possible, it is still useful to intervene at any point after the outbreak has been recognized and before all susceptible
