Interrupting the transmission of infectious agents by introducing new vaccines into a population and creating herd immunity has proven to be a remarkable hidden genie for vaccine effectiveness. For example, oneto two-thirds of the effectiveness of the bacterial conjugate vaccines is linked to protection of the unvaccinated. However, the mechanisms of herd immunity are often not well understood,...

Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in th...

BACKGROUND In 2002, vaccination with a serogroup C meningococcal conjugate vaccine (MenC) was introduced in the Netherlands for all children aged 14 months. Despite its success, herd immunity may wane over time. Recently, a serogroup A,C,W135,Y meningococcal conjugate vaccine (MenACWY) was licensed for use in subjects of 12 months of age and above. OBJECTIVES To evaluate the cost-effectivenes...

OBJECTIVE To evaluate the cost-effectiveness of implementing a universal infant 7-valent pneumococcal conjugate vaccine (PCV7) vaccination program in the Irish health-care setting from the health-care payers' perspective. METHODS A model was constructed in MS Excel to follow a cohort of vaccinated and unvaccinated individuals from birth over a 5-year period. The reduction in events that would...

Several aspects of the dynamics of Coxiella burnetii that are relevant for the implementation of control strategies in ruminant herds with endemic Q fever are unknown. We designed a longitudinal study to monitor the dynamics of exposure to C. burnetii in a red deer herd with endemic infection in order to allow the design of Q fever-specific control approaches. Other relevant aspects of the dyna...

To the Editor—Dominguez et al. [1] described outbreaks of measles occurring in Catalonia despite good vaccination rates. The way in which heterogeneity in the distribution of nonimmune individuals diminishes herd immunity can be explained using network simulation models. Herd immunity is the indirect impact of vaccination on an epidemic. This effect is caused by having a sufficient number of im...