gb‐da Cunha 2002.

Study characteristics
Methods	Case‐only ecological method. Study to determine if there is an increased risk of acute aseptic meningitis and mumps in children aged 1 to 11 years in 2 regions of Brazil, Mato Grosso do Sul and Mato Grosso (MS and MT).
Participants	Children aged 1 to 11 years old irrespective of previous vaccination. MS (N = 473,718); MT (N = 580,587). The campaigns started in mid‐August 1998 in MS, and in late September in MT, and lasted for 1 month. The reported numbers of children vaccinated were 442,962 (coverage of 93.5%) and 402,927 (coverage of 69.4%), respectively. Most doses were applied in the first 2 weeks of the campaigns.
Interventions	MMR vaccine containing Leningrad‐Zagreb mumps strain (Serum Institute of India Ltd)
Outcomes	Notification of meningitis is statutory in Brazil, with a standardised form completed for each case. Aseptic meningitis (clinical diagnosis or notification form). 31 (in MT) or 37 (in MS) weeks before and 10 weeks after vaccination campaign
Funding Source	Government
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
COEM ‐ case selection	Low risk	Adequate ‐ medical record
COEM ‐ exposure	Unclear risk	There was insufficient information.
COEM ‐ time trend comparison	Low risk	Adequate ‐ well‐defined period
COEM ‐ comparability	Unclear risk	There was insufficient information.
Summary Risk of Bias assessment	Unclear risk	We had concerns regarding at least 1 domain such that some doubt is raised about the results.