ba‐Castilla 2009.

Study characteristics
Methods	Case‐control study ‐ Navarre, Spain
Participants	The cases were all children residing in Navarre born between 1998 and 2005 who had a diagnosis of mumps confirmed microbiologically or epidemiologically between August 2006 and June 2008. Cases occurring before age 15 months were excluded, as were those whose paediatrician could not be identified. For each case, 5 individually matched controls were selected amongst children with the same sex, municipality, district of residence, and paediatrician. Matching was performed by selecting controls with the closest birth date within the same calendar semester to the corresponding case. We excluded as controls those children who had been diagnosed with mumps before the date the case was diagnosed or who had not fulfilled all the pairing criteria since the beginning of 2006; these children were replaced with the next child who met the inclusion criteria. Cases (N = 241): children aged 1 to 10 years with confirmed (laboratory or epidemiologically) mumps with symptoms of disease between August 2006 and June 2008 Controls (N = 1205): children matched for sex, municipality, district of residence, and paediatrician
Interventions	MMR vaccine prepared with Jeryl Lynn mumps strain
Outcomes	Exposure to MMR vaccine at least 30 days before mumps onset
Funding Source	Government
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
CCS ‐ case selection	Low risk	Adequate ‐ clinically or laboratory‐confirmed
CCS ‐ control selection	Low risk	Adequate ‐ community
CCS ‐ comparability	Low risk	Adequate ‐ matched by sex, birth date, district of residence, and paediatrician
CCS ‐ exposures	Low risk	Adequate ‐ secure record ‐ blinded review
Summary Risk of Bias assessment	Low risk	Plausible bias is unlikely to have seriously altered the results.