13. Safety: aseptic meningitis.

Study ID and design	Population	Outcome definition	Exposure MMR/MMRV vaccine	Findings	Crude data	Estimate (95% CI)
bb‐Black 1997 Matched case‐control	Cases n = 59 Controls n = 118 (age 12 to 23 months at the time of discharge diagnosis, between 1984 and 1993). For each ascertained case, 2 controls matched for age, sex, HMO, and HMO membership status were selected.	Aseptic meningitis Potential cases of aseptic meningitis were identified by computerised hospitalisation at 4 HMOs that participated in the Vaccine Safety Datalink project. They were children aged 12 to 23 months with ICD‐9 discharge diagnoses 045.2, 047.*, 048, 072.1, 321.2 or 322.* between 1984 and 1993. Medical records of potential cases were reviewed and included as cases when corresponding to validation criteria (see column on the right). No evidence of prior underlying meningitis or underlying disease caused by toxoplasmosis, syphilis, cytomegalovirus, neonatal herpes simplex, or HIV. (The same exclusion criteria were used for controls.) In addition, bacterial, mycobacterial, and fungal cultures of the cerebrospinal fluid must have been negative, and the patient must have had a cerebrospinal fluid white blood cell count of >= 10 cells/mm3.	MMR vaccine: Jeryl Lynn mumps strain. Any vaccines includes: Hib: Haemophilus influenzae type b, DPT: diphtheria‐pertussis‐tetanus toxoids, OPV: oral polio vaccine, HDPT: Haemophilus influenzae type b diphtheria pertussis tetanus toxoid vaccine, HepB: hepatitis B vaccine Vaccine and time window (a) MMR 0 to 14 days (b) MMR 0 to 30 days (c) MMR 8 to 14 days (d) Any vaccine 0 to 14 days (e) Any vaccine 0 to 30 days (f) Any vaccine 8 to 14 days Vaccination status of both cases and controls was derived from medical record review.	In this analysis of hospitalisation caused by AM, there was no increased risk of AM after MMR vaccine containing Jeryl Lynn strain mumps.	N cases vaccinated/ N cases versus N controls vaccinated/ N controls (a) 1/59 versus 4/118 (b) 3/59 versus 7/118 (c) 1/59 versus 2/118 (d) 2/59 versus 8/118 (e) 7/59 versus 18/118 (f) 2/59 versus 4/118	OR (95% CI) (a) 0.50 (0.1 to 4.5) (b) 0.84 (0.2 to 3.5) (c) 1.00 (0.1 to 9.2) (d) 0.44 (0.1 to 2.1) (e) 0.75 (0.3 to 1.9) (f) 1.00 (0.2 to 5.6)
eb‐Park 2004 Case cross‐over	(1) n = 39. Children with aseptic meningitis aged 13 to 29 months of both sexes, vaccination date confirmed by vaccination record. (2) n = 19. Children with aseptic meningitis aged 12 to 15 months of both sexes, vaccination date confirmed by parents only.	Aseptic meningitis Generically defined as syndrome characterised by acute onset of meningeal symptoms, fever, and cerebrospinal fluid pleocytosis, with bacteriologically sterile cultures. Cases of aseptic meningitis were identified from insurance claims and hospitalisation data during 1998 in Korea. Authors considered cases corresponding to diagnosis criteria occurred in children aged 8 to 36 months who had received MMR vaccine within 1 year before disease onset and for whom vaccination records were available.	MMR vaccine: Strain type not stated (the study was conducted in the same setting of the study eb‐Ki 2003; both studies were performed in Korea, where MMR vaccine containing Urabe or Hoshino mumps strain was routinely administrated in public health, and MMR vaccines containing the Jeryl Lynn or Rubini in the private sector). Risk period (42 days) (a) from disease onset date to 42 days after Control period (323 days) (b) from 42 days up to 365 days after disease onset	Study results showed that risk increased in the third week after vaccination and was elevated until the sixth week.	(a) versus(b) (1) 11 versus 28 cases (2) 5 versus 14 cases Sensitivity analysis n = 58, 16 versus 42 cases	RR (95% CI)(*) (1) 3.02 (1.50 to 6.08) Sensitivity analysis 2.93 (1.65 to 5.22) (*)Mantel‐Haenszel estimator Under the null hypothesis, this estimator is directly analogous to the Mantel‐Haenszel OR for matched‐pair case‐control study.
eb‐Ki 2003 Case cross‐over	67 children, mean age 19.1 months (standard deviation = 5.4 months)	Aseptic meningitis Aseptic meningitis is a syndrome characterised by acute onset of meningeal symptoms, fever, and cerebrospinal fluid pleocytosis with bacteriologically sterile cultures. The following criteria were used to define eligible cases of aseptic meningitis for the study: 1) Korean insurance claim cases based on the ICD‐10 (codes A87.9, G03.0, G03.9, and G02.0); and 2) cerebrospinal fluid pleocytosis (leukocytes ≥ 5) with bacteriologically sterile cultures (if measured); or 3) neck stiffness and/or convulsions, or 2 other symptoms (headache or vomiting) in addition to a fever (≥ 38.0 °C, if measured). Patients’ charts were reviewed and their symptoms, laboratory tests, and last diagnoses on the discharge record checked. If patients were diagnosed with aseptic meningitis and were hospitalised in a general hospital, in accordance with these criteria, those who had headache, fever, and vomiting could be included as participants.	MMR vaccine (1) n = 29 MMR with Urabe or Hoshino mumps strain (2) n = 38 MMR with Jeryl Lynn or Rubini mumps strain Risk period (42 days) (a) from disease onset date to 42 days after Control period (323 days) (b) from 42 days up to 365 days after disease onset	Study results showed that no significant risk was associated with the Jeryl Lynn or Rubini strain of the vaccine. For the Urabe or Hoshino strain, the risk increased in the third week after vaccination and was elevated until the sixth week.	(a) versus(b) (1) 13 versus 16 cases (2) 3 versus 35 cases	RR (95% CI)(*) (1) 5.5 (2.6 to 11.8) (2) 0.6 (0.18 to 1.97) (*)Mantel‐Haenszel estimator Under the null hypothesis, this estimator is directly analogous to the Mantel‐Haenszel OR for matched‐pair case‐control study.
db‐Makela 2002 Person‐time cohort	Children immunised aged 1 to 7 years old. Between November 1982 and September 1986 n = 535,544 n = 120 children hospitalised for encephalitis (MMR vaccine was administered before the disease), and only 64 between 0 and 24 months after MMR vaccination.	Aseptic meningitis Inflammation of the meninges. Usually a self‐limiting disease of known or suspected viral cause consisting of fever, headache, signs of meningeal irritation, without evidence of brain parenchymal involvement and a lymphocytic and mononuclear pleocytosis of CSF. The term 'meningoencephalitis' does not differentiate cases with prominent involvement of the brain parenchyma from those with meningeal involvement only. Hospitalisation records (ICD‐8 codes: 045.99, 320.88, 320.99) and review of patients' medical records to assess correspondence to case definition.	Exposure risk period: (a) 0 to 3 months after vaccination Control period: (b) 4 to 24 months after vaccination Observation period: (c) 0 to 24 months after vaccination MMR II vaccine (Merck & Co, West Point, PA) Measles: Enders‐Edmonston Mumps: Jeryl Lynn Rubella: Wistar RA 27/3 Vaccination data were assessed through vaccination register.	Not significant excess of hospitalisation within 3 months of vaccination (P = 0.57) The incidence of meningitis of undefined causes in 1‐ to 7‐year‐old children decreased from 10.17 per 100,000 in 1983 to 7.71 per 100,000 in 1985.	(a) 10 cases (3 months) (b) 54 cases (21 months) (c) 64 cases (24 months)	rr (95% CI)(*) 1.30 (0.66 to 2.55) (*)rate ratio amongst risk (a) and control (b) period
db‐Dourado 2000 Self‐controlled case series ‐‐‐‐‐‐‐‐‐‐‐‐‐ Case‐only ecological method	Children aged 1 to 11 years (from census) n = 452,344 n = 129 children aged 1 to 11 years old admitted to the referral hospital with a diagnosis of aseptic meningitis between 10th and 43rd epidemiologic surveillance weeks of 1997 (March to October). n = 87 fulfilled inclusion criteria; n = 29 cases of AM occurred prior to the mass immunisation campaign; n = 58 after the immunisation campaign. Of the 58 children, n = 50 were know to have been vaccinated. (The date of vaccination was available for 43 of these children.)	Aseptic meningitis Data about meningitis were obtained from the state Epidemiology Surveillance System and from the neurologic service of the state referral hospital for infectious disease (Hospital Couto Maia), by reviewing hospital records of children admitted between the 10th and 43rd epidemiological surveillance weeks. Demographic, clinical, and laboratory data were collected on a standardised form. Inclusion/exclusion criteria 1) Residence in the city of Salvador 2) Age 1 to 11 years 3) Cerebrospinal fluid with a cell count of > 10 and < 1200 cells per mL (higher counts could be attributed to unconfirmed bacterial meningitis) 4) Predominance of lymphocytes in the cerebrospinal fluid of > 50% of the total number of cells 5) Exclusion of any bacteriologic or fungal confirmation through the use of Gram stain, latex, immunoelectrophoresis, stain for Cryptococcus neoformans, Ziehl‐Neelsen stain, or culture for bacteria and Mycobacterium tuberculosis 6) Exclusion of all cases with a history of prior meningitis or any neurologic disorder and any cases with sepsis, pneumonia, otitis, or any other disease that might be associated with an increased cell count in the cerebrospinal fluid	Self‐controlled case series Exposure risk period: (a) 3 to 5 weeks after vaccination (i.e. 15 to 35 days) Control period: (b) 1 to 2 weeks and 6 to 10 weeks after vaccination Observation period: (c) 1 to 10 weeks after vaccination ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Case‐only ecological method (a) Reference period (pre‐vaccination): 10 to 32 epidemiologic surveillance weeks; time interval = 23 weeks (b) Low‐risk period: 34 to 35 epidemiologic surveillance weeks; time interval = 2 weeks (c) High‐risk period: 36 to 39 epidemiologic surveillance weeks (3 to 6 weeks after vaccination day) time interval = 4 weeks (d) Low‐risk period: 40 to 43 epidemiologic surveillance weeks; time interval = 3 weeks MMR vaccine Pluserix vaccine (SmithKline Beecham, UK) containing mumps Urabe strain Vaccination began on 16 August 1997 (National Immunisation Day, surveillance week 33), 45% coverage of the target population was achieved on that day, high coverage (exact data not reported, but very close to 100%) during the 2 following weeks. Vaccination history was obtained by vaccination cards or visits/phone call.	An elevated risk of aseptic meningitis was observed 3 weeks after Brazil's national vaccination day compared with the risk in the pre‐vaccination period. This result was confirmed by a case series analysis.	(a) 35 cases (b) 3 and 5 cases (c) 43 cases ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Cases/PT (weeks) (a) 29/10,403,912 (b) 3/904,688 (c) 46/1,809,376 (d) 9/1,809,376	Self‐controlled case series rr (95% CI)(*) 30.4 (11.5 to 80.8) (*)Poisson regression ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Case‐only ecological method rr (95% CI)(**) (a) reference weeks (b) 1.19 (0.36 to 3.91) (c) 9.12 (5.73 to 14.52) (d) 1.78 (0.84 to 3.77) (**)rate ratio amongst risk periods: (b), (c), (d) and control period (a).
gb‐da Cunha 2002 Case‐only ecological method	Children aged 1 to 11 years State of Mato Grosso do Sul (MS) n = 580,587 State of Mato Grosso (MT) n = 473,718	Aseptic meningitis Data on cases of meningitis were obtained from the routine surveillance system in both states. Notification of meningitis is statutory in Brazil, with a standardised form completed for each case. The attending physician or nurse completes the notification form in the health facility where the diagnosis is made. The notification form includes data on patient’s identification, clinical diagnosis, evolution, treatment, results of vaccination status, and laboratory investigations (the last 2 items not always reported). Reported cases of meningitis were classified into aseptic or not based on information from the notification forms, using 2 different criteria, which are independent but non‐exclusive. In both criteria, AM included only cases with absence of a positive bacteriological isolate in culture or stain of CSF and did not have a positive blood culture or mention of other non‐viral aetiology. Criterion 1: If the diagnosis in the form was of viral aetiology or unknown aetiology, cases were classified as AM. They were classified as not having AM if they had a suspected or confirmed diagnosis of meningitis by a known (non‐viral) agent through any laboratory or clinical finding. Criterion 2 (laboratory): Cases were considered AM if they had a CSF with the following findings: cell count greater than 10 and less than 1500 and presence of lymphocytes greater that 49%. (Applied for the cases in which laboratory data were present in the notification forms. In their absence, cases were excluded.)	(MS) Unexposed period (a) reference weeks 1 to 31 (MS) Exposed period (b) low‐risk weeks 32 to 34 (c) high‐risk weeks 35 to 37 (d) low‐risk weeks 38 to 42 (e) all weeks 32 to 42 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MT) Unexposed period (a) reference weeks 1 to 37 (MT) Exposed period (b) low‐risk weeks 38 to 40 (c) high‐risk weeks 41 to 43 (d) low‐risk weeks 44 to 48 (e) all weeks 38 to 48 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ MMR vaccine: Serum Institute of India, Ltd, Pune. Contained Leningrad‐Zagreb mumps strain. 3 different lots were used in each state (MS and MT). Vaccination began in mid‐August 1998 (week 32) in MS and late September in MT (week 38), and lasted for about 1 month, even if the most part of the doses had been administered during the first 2 campaign weeks. Vaccination was reported for 69.4% and 93.5% of the target population in MT and in MS, respectively.	This study shows an increase in number of notified cases of AM in the 2 states studied, 3 to 4 weeks after the MIC using Leningrad‐Zagreb mumps strain MMR vaccine (3 to 4 weeks after the MIC corresponding to incubation period for wild mumps infection, and the increase was restricted to the age group targeted by the campaign and to the aseptic form of meningitis). The use of the vaccine on a large scale over a short period of time made it possible to identify an increase in risk which may be present, but more difficult to measure when vaccination is spread over longer periods. The risk estimates varied depending on the diagnostic criteria used and the state. There was also an increase in the incidence of notified mumps after the campaign in the state where data were available.	cases/PT (weeks) (MS) AM criterion 1 (a) 22/14,685,258 (b) 7/1,421,154 (c) 35/1,421,154 (d) 6/2,368,590 (e) 48/5,210,898 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MT) AM criterion 1 (a) 71/21,481,719 (b) 7/1,741,761 (c) 71/1,741,761 (d) 25/2,902,935 (e) 103/6,386,457 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MS) AM criterion 2 (a) 8/14,685,258 (b) 4/1,421,154 (c) 24/1,421,154 (d) 2/2,368,590 (e) 30/ 5,210,898 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MT) AM criterion 2 (a) 36/21,481,719 (b) 3/1,741,761 (c) 54/1,741,761 (d) 15/2,902,935 (e) 72/6,386,457	rr (95% CI)* (MS) AM criterion 1 (a) reference weeks (b) 3.3 (1.41 to 7.7) (c) 16.4 (9.65 to 28.0) (d) 1.7 (0.69 to 4.2) (e) 6.2 (3.71 to 10.2) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MT) AM criterion 1 (a) reference weeks (b) 1.2 (0.56 to 2.6) (c) 12.3 (8.88 to 17.1) (d) 2.6 (1.65 to 4.1) (e) 4.9 (3.61 to 6.6) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MS) AM criterion 2 (a) reference weeks (b) 5.2 (1.56 to 17.2) (c) 31.0 (13.93 to 69.0) (d) 1.6 (0.33 to 7.3) (e) 10.6 (4.84 to 23.1) ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (MT) AM criterion 2 (a) reference weeks (b) 1.0 (0.32 to 3.3) (c) 18.5 (12.13 to 28.2) (d) 3.1 (1.69 to 5.6) (e) 6.7 (4.51 to 10.0) (*)rate ratio amongst exposed (risk) periods: (b), (c), (d), (e) and unexposed period (a)
gb‐da Silveira 2002 Case‐only ecological method	Children aged 1 to 11 years target population n = 110,629 (Rio Grande do Sul) dose	Aseptic meningitis Any‐cause AM was defined as: occurrence of clinically diagnosed meningitis in a person with a CSF pleocytosis (between 5 and 1500 leucocytes/mL) and a negative Gram stain. Viral isolation is not routinely performed in Rio Grande do Sul. Mumps‐associated AM was defined as: that occurring in conjunction with or following clinically diagnosed mumps. Vaccine‐associated AM was defined as: aseptic meningitis with a pleocytosis of 10 to 1500 leukocytes/mL and occurring within 15 to 35 days after vaccine receipt.	MMR vaccine: produced by Serum Institute of India, Lot: 180‐X: measles: Edmonston‐Zagreb; mumps: Leningrad‐Zagreb; rubella: Wistar RA 27/3. The campaign was conducted between 8 September and 28 November 1997; weeks 37 to 48. (a) unexposed period in 1995/1996 39 to 47 weeks (b) unexposed period in 1997 1 to 38 weeks (c) exposed period in 1997: High risk: 39 to 47 weeks (d) exposed period in 1997: Low risk: 48 to 53 weeks	A total of 105,098 doses of Leningrad‐Zagreb were administered to children aged 1 to 11 years, for an overall coverage of 95%. The risk of vaccine‐associated aseptic meningitis (31 cases) was 2.9 cases per 10,000 doses of Leningrad‐Zagreb administered (equivalent to 1 case per 3390 doses administered). Within the 1‐ to 11‐years age group, the risk did not differ significantly by age group. These findings suggest that Leningrad‐Zagreb is more reactogenic than Urabe and Jeryl‐Lynn strains.	(a) 2.4 cases per 100,000 person weeks; 4.5 cases in average (b) 10 cases (any cause) (c) 28.7 per 100,000 person weeks 31 cases vaccine associated (55 any cause, 41 vaccinated) (d) 4 cases (any cause)	rr (95% CI) (c) 12.2 (6.0 to 24.7)(*) (*)rate ratio (c) and (a)
db‐Farrington 1995 Self‐controlled case series	Children aged 12 to 24 months discharged from hospital in 5 districts in England (Ashford, Leicester, Nottingham, Preston, and Chorley & Ribble) for varying periods between October 1988 and February 1993. Readmissions within 72 h with the same diagnosis were counted as 1 episode. n = 952 children	Aseptic meningitis Children discharged from hospital with a diagnosis of: meningitis categorised as mumps, aseptic, or viral (ICD 072.1, 047., 321.) Children aged between 366 and 730 days.	MMR vaccine: Urabe mumps strain Jeryl Lynn mumps strain Rubella strain not specified. Exposure risk period: (a1) 6 to 11 days (1 to 2 weeks after vaccination) (a2) 15 to 35 days (3 to 5 weeks after vaccination) (Urabe strain) Control period: (b) for each vaccine was defined as the time not included in a risk period. The analyses were adjusted for age and were grouped in 6 equal intervals of about 2 months.	The study shows that there is a true risk of a neurological event attributable to the Urabe strain.	Urabe strain (a1) 0 cases (a2) 5 cases	rr (95% CI) (a2) 38.1 (4.3 to 336)(*) (*)Poisson regression
db‐Miller 2007 Self‐controlled case series	Children aged 12 to 23 months with discharge diagnosis of febrile convulsion or aseptic meningitis	Aseptic menigitis: Viral meningitis (A87), mumps (B26), meningitis in other infections classified elsewhere (G02), and meningitis due to other and unspecified causes (G03) were identified for the period 1 May 1998 to 30 June 2001, and case notes were reviewed by a paediatrician. In addition, computerised hospital records for children aged 12 to 23 months with an ICD‐9 discharge diagnosis of meningitis categorised as mumps, aseptic, or viral (072.1, 047, 321) were identified for the period 1 January 1991 to 30 September 1992, prior to the withdrawal of Urabe‐containing MMR vaccines, and were linked with MMR vaccination histories. Cases of laboratory‐confirmed mumps meningitis were also ascertained from reports made to the Centre for Infections from laboratories in England and Wales for the period of October 1992 to the end of June 2004.	MMR vaccine: (1) MMR with Urabe mumps strain up to September 1992 (2) MMRII (Sanofi Pasteur) Edmonston‐Enders measles strain, Jeryl Lynn mumps strain, between September 1992 and May 1998 (3) MMR Priorix (GlaxoSmithKline) Schwarz measles strain RIT4385 (Jeryl Lynn) from May 1998 Exposure risk period: (a) 15 to 35 days after vaccination (from May 1998 to June 2001) (Urabe MMR) (b) 15 to 35 days after vaccination (from January 1991 to September 1992) (Jeryl Lynn MMR) MMR vaccination histories were independently obtained through linkage with computerised immunisation records in the 2 Thames regions, using either the National Health Service number or sex, date of birth, and post code, a highly specific linking algorithm. Information on batch number was sought for any confirmed aseptic meningitis cases with onset 15 to 35 days after MMR vaccination. The formatting of batch numbers differs substantially between manufacturers in length and alphanumeric coding and is a precise means of distinguishing between vaccines from different manufacturers.	Before after between 2 risk periods, re‐analysis of the data presented in db‐Farrington 1995 This study confirms that the risk of aseptic meningitis with Priorix vaccine, if it exists at all, is significantly lower than with Urabe‐containing mumps vaccine. The study allowed the exclusion of risks as rare as 1 in 437,000 for laboratory‐confirmed mumps meningitis with non‐Urabe‐containing MMR vaccines.	Comparison between 2 risk periods Aseptic meningitis (a) 4 cases (b) 0 cases ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Laboratory‐confirmed mumps‐positive cerebrospinal fluid (a) 16 cases (b) 0 cases Data from the paper db‐Farrington 1995	rr(95%CI) 25.9 (2.8 to 233)(*) (*) rate ratio (a) versus (b)
db‐Perez‐Vilar 2018 Self‐controlled case series	For this study, WHO selected 26 sentinel sites (49 hospitals) distributed in 16 countries of the 6 WHO regions. The study population included children ages 9 to 23 months admitted to a network‐participating hospital during January 2010 to March 2014, with a discharge diagnosis of either AM or immune thrombocytopenic purpura.	Aseptic meningitis probable cases ICD‐9 codes in first discharge diagnosis position: 047 (047.0 to 047.9) Meningitis due to enterovirus 049.0 to 049.1 Other non‐arthropod‐borne viral meningitis 072.1 Mumps meningitis 321.2 Meningitis due to viruses not elsewhere classified 322.0, 322.1, 322.9 Meningitis of unspecified cause ICD‐10 codes in first discharge diagnosis position: A87.0 Meningitis due to enterovirus A87.1 Adenoviral meningitis A87.2 Lymphocytic choriomeningitis A87.8 Other viral meningitis A87.9 Viral meningitis, unspecified B26.1 Mumps meningitis G02.0 Meningitis due to viruses not elsewhere classified G03.0, G03.8, G03.9 Meningitis of unspecified cause	Vaccine(measles strain) (mumps strain) Priorix, GSK (Schwarz) (RIT 4385a) Priorix‐Tetra, GSK (Schwarz) (RIT 4385a) MMR Shanghai Institute (Shanghai‐191) (S79) Measles, Lanzhou Institute (Shanghai‐191) (–) Measles‐Rubella, Beijing Tiantan (Shanghai‐191) (–) M‐M‐R‐II, MSD (Enders’ Edmonston) (Jeryl Lynn (Level B)) MMR, Razi Vaccine and Serum Research (AIK‐C) (Hoshino) M‐M‐RVAXPRO, Sanofi Pasteur‐MSD (Enders’ Edmonston) (Jeryl Lynn (Level B)) Trimovax, Sanofi Pasteur (Schwarz) (Urabe AM9) Measles, Serum Institute of India Pvt. (Edmonston‐Zagreb) (–) Measles‐Rubella, Serum Institute of India Pvt. (Edmonston‐Zagreb) (–) MMR, Serum Institute of India (Edmonston‐Zagreb) (Leningrad‐Zagreb) Tresivac, Serum Institute of India (Edmonston‐Zagreb) (Leningrad‐Zagreb) Rouvax, Sanofi Pasteur (Schwarz) (–) Risk period 8 to 35 days Washout periods 1 to 7 days 36 to 42 days Control period 43 to 84 days	The elevated risk estimates found for the Leningrad‐Zagreb mumps strain are consistent with previous studies (gb‐da Cunha 2002; gb‐da Silveira 2002). Regarding Jeryl‐Lynn‐derived strain vaccines, although the study did not have enough power to confirm the absence of risk for these strains, the finding of zero cases in the risk window was consistent with the hypothesis of no association (bb‐Black 1997; db‐Makela 2002).	In 16 countries n = 84 confirmed aseptic menigitis cases (Risk versuscontrol) period (a) Overall risk of AM following mumps‐containing vaccines (35 versus 5) (b) Overall risk of AM following mumps‐containing vaccines (excluding cases from Iran) (22 versus 3) (c) Leningrad‐Zagreb strain (7 versus 1) (d) Vaccines products used Hoshino/Leningrad‐Zagreb/Urabe AM9 (27 versus 2) (e) Vaccines products used Hoshino/Leningrad‐Zagreb/Urabe AM9 (excluded cases from Iran) (14 versus 0)	rr (95% CI) adjusted (a) 10.8 (4.0 to 29.2) (b) 12.4 (3.1 to 49.1) (c) 6.4 (1.3 to 87.4) rr (95% CI) unadjusted (d) 20.3 (48 to 85.2) (e) not estimable

AM: aseptic meningitis
CI: confidence interval
CSO: cerebro‐spinal fluid
HMO: health maintenance organisation
ICD‐10: International Classification of Diseases
incidence: cases/PT
MIC: mass immunisation campaigns
MMR: measles, mumps, rubella vaccine
MMRV: measles, mumps, rubella, and varicella vaccine
n: number of participants
OR: odds ratio
PT: person‐time
rr: rate ratio (relative incidence, incidence rate ratio)
RR: risk ratio (relative risk)
WHO: World Health Organization