Description of selected observational studies on HZ incidence in populations with a widespread chickenpox vaccination program.

<p><i>HMO</i> health maintenance organization; <i>HZ</i> herpes zoster; <i>CP</i> chickenpox; <i>RR</i> relative risk; <i>PY</i> person-years; <i>MMDS</i> Melbourne Medical Deputising Service; <i>ER</i> emergency room.</p>§<p>Descriptions of vaccination uptake are as reported in the respective original papers.</p>*<p>H = High: the quality of methods used in this paper permits the results, within the scope of the study design, to be interpreted with at the most a few remarks. M = Medium: the quality of methods used in this paper permits the results, within the scope of the study design, to be interpreted, but with some caution. L = Low: the quality of methods used in this paper urges the reader to interpret the results, even within the scope of the study design, with sufficient caution.</p><p>£See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066485#pone.0066485.s002" target="_blank">Table S2</a>.</p>**<p>The ‘B’ statement expresses whether the study supported the existence of exogenous boosting (‘+) or not (‘−’).