ca‐Chang 2015.

Study characteristics
Methods	Cohort study ‐ China ‐ conducted in 13 classes that had secondary cases of rubella. Using the secondary attack rates, the study authors evaluated VE by the number of RCV doses received and age at vaccination.
Participants	School A is a middle school with a total of 1621 students enrolled in the 7th, 8th, and 9th grades, with a total of 37 classes. All students are day students, and they eat their meals at home. The school canteen only provides meals for some teachers. No school bus is available to students. This school has no full‐time school doctor, only a part‐time health teacher. Students were born between 1998 and 2001.
Interventions	MMR (BRD‐II or RA27/3) A BRD‐II rubella strain vaccine was developed in the 1980s in China, and has been available in the Chinese private market since 1993. All monovalent rubella and measles and rubella combined (MR) vaccines in use in China are based on the BRD‐II rubella strain. A domestic measles, mumps, and rubella combined vaccine (MMR) based on BRD‐II strain has been available in China’s private market since 2003. An imported RA27/3 strain‐based vaccine is also available in China.
Outcomes	Probable rubella case: defined as a suspected rubella case with fever > 37.5 °C and at least 1 of the following symptoms: arthralgia, arthritis, lymphadenopathy, or conjunctivitis. A laboratory‐confirmed case: required a positive serologic test for rubella IgM antibody. Epidemiologically linked case: confirmed case was defined as a suspected case or a probable case that was not laboratory confirmed, but that was geographically and temporally related to a laboratory‐confirmed case.
Funding Source	Government
Notes	Conclusions: the rubella vaccines used in China that are based on the BRD‐II rubella vaccine strain have a VE of 94%, which is similar to the more commonly used RA27/3‐based RCVs. Low vaccination coverage contributed to this outbreak; early reporting of an outbreak is necessary for effective outbreak response immunisation.
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ exposed cohort selection	Low risk	Adequate ‐ secure record ‐ vaccination record
PCS/RCS ‐ non‐exposed cohort selection	Unclear risk	There was insufficient information.
PCS/RCS ‐ comparability	Unclear risk	Probably adequate ‐ age 11 to 13 ‐ probable residual confounding
PCS/RCS ‐ assessment of outcome	Low risk	Adequate ‐ laboratory‐confirmed
Summary Risk of Bias assessment	Unclear risk	We had concerns regarding at least 1 domain such that some doubt is raised about the results.