ca‐Wichmann 2007.

Study characteristics
Methods	Retrospective cohort study
Participants	Students between 10 and 21 years of age (Duisburg, Germany) n = 1098 10 to 12 years old (N = 485); 13 to 15 years old (N = 460); 16 to 21 years old (N = 152)
Interventions	MMR, but it is unclear if all study population were immunised with only MMR or other single‐component vaccines. Effectiveness of vaccination in preventing measles during an outbreak
Outcomes	Measles cases were identified according to a standard clinical case definition.
Funding Source	Government
Notes	Authors' conclusions: VE was high. Vaccination coverage (92% 1 dose and 70% 2 doses) was insufficient to prevent the outbreak. Immunisation gaps were found, especially in older students. To prevent further outbreaks and to achieve the goal of measles elimination in Germany, vaccination coverage must be increased.
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ exposed cohort selection	Low risk	Adequately defined ‐ by vaccination record ‐ representative of the exposed
PCS/RCS ‐ non‐exposed cohort selection	Low risk	Adequately defined ‐ by vaccination record ‐ drawn from the same community
PCS/RCS ‐ comparability	Unclear risk	Possible residual confounding ‐ no information about possible confounders
PCS/RCS ‐ assessment of outcome	Unclear risk	By questionnaire ‐ in this study 88% of students returned completed questionnaires
Summary Risk of Bias assessment	Unclear risk	We had concerns regarding at least 1 domain such that some doubt is raised about the results.